Let's jump ahead a bit to 1962 and see what Bender (that's Al.... Al... no not Bundy, Albert - no not Bender from Futurama either...) has to say about his own experiences, specifically who and what the saucers are, & why it's now okay about 5 years later to tell what he knows; after being silenced by these 3 MIB's.
Hmm a little side note about Futurama... Some of the names come from these early saucer peeps: Fry, Bender... seems like there's more but I'm drawing a blank at the moment...

p23 - Author is visited by an unseen entity, surrounded by a bluish light & the smell of sulfur ie brimstone. Reads like a demonic entity, or what were taken for demons in bible times; whatever they might actually be. Genies (djinn), etherians, stupid angels... The djinn are supposed to be older than man and want their planet back.
The nauseous odor could be the burning of the air during a mat or demat, as the materializing form displaces the surrounding air. This same odor accompanies almost all the monster sightings. Sorry you sasquatch hunters, these guys are from another dimension, you'll never catch one.
These guys don't want to be investigated, they don't want the world to know about them.
Still no abductions, no greys, no missing time; although flipping through one of Timothy Good's books he has a photo of a guy who experienced missing time in 1951, right around the time of the events in this book. Another onion in the ointment for my no-ET hypothesis; if that story is true - will find out later when I get to his books, they're at the bottom of the pile.
p32 - Pauline Peavy, a medium who claimed to be in touch with aliens. She "communicated telepathically" & said they were Valkyries, world saviors.
Other names mentioned as "helpers" to his org are Criswell (of Plan 9 fame), Wilson Tucker (sci-fi author - I read one of his books once I believe), Meade Layne, Coral Lorenzen.
p36 - MIB appears in theater, with glowing eyes, sitting right next to him. No odor though. Different visitor than the bluish light guy?! Bender doesn't say so. Guess not...
p42 - Dominick Lucchesi has plans to build a working saucer, without using anti-grav. Supposedly. I don't think they ever built it. "Complete technical data necessary to construct a vehicle that would fulfill all requirements." Speeds limited by friction. This guy thinks reported saucer speeds are exaggerated. Electro-gravitics can create a friction shield though; see LaV & his theory on the B-2 wings being electrified to create such a shield.
Author does not follow up with claim of home-made saucer plans. So far, maybe later in the book...
p44 - Connection between Mars & ufos. During opposition ufos are more numerous. Is this proof they come from there, as these guys seem to think? Or is there some kind of gravitational anomaly that occurs at that time that makes them easier to fly here on earth?
p49 - Entity again; bluish light, sulfur odor, glowing eyes... Could it be Mothman? Don't recall BO issues with Mothman though...
p53 - Layne tells them about Adamski.
p55 - Letters from Adamski. He complains Layne got details in the story wrong. Or is Adamski changing the story & got mad cuz the earlier version (brief summary - Orthon spoke English, for example) got published?
Adamski says he "knows" the spacemen are interplanetary. - That's what they want him to think; the story is being set up.
Maybe the test about whether or not a "spaceman" will contact you is how gullible you are. If you
want to believe...
These fake spacemen visiting the Adamski's of the world would be the CIA guys. Don't think the Bender-type visitations can be faked; they would be real (djinn, working with or for the black ops dudes - but who controls who)... Yikes. But why the warning, why the Silence Group as someone starts calling them soon... It seems like they don't want the fake ET thing exposed, they want it to go on. They want peeps to believe in the ET's. But why would these "demon" guys want that? Exposure of the con would affect them... how? Are these 2 forces opposed or working together? So who would the good guys be then? Seems the demon guys, the MIB & the fake space brothers are all in it together; what would the opposition good guy group be? Unless some of the space brothers aren't fakes... Which ones?
Why does Bender see blue lights not red? Most ufos show red haze. Blue lights would be higher frequency as in UV end of the spectrum; Layne's etherians then. What about the red lights phenomena? At the low end of the spectrum; infrared. Is this significant? Maybe one of these authors will touch on this eventually...
p58 - Another version of Mantell story. Wreckage scattered for a mile. Double-check this maybe, accounts vary as to wreckage.
Fred Reagan saved by saucer that wrecked his plane. He was free-falling, it took him aboard, he hazily saw giant metallic asparagus guys (! cool!), passed out & woke up to brimstone odor & blue light, then came to in the hospital. He had landed on the ground, uninjured. Except that he shortly died of massive radiation overdose. Now the giant veggies did save him, but then we have the blue-light guys with super BO again. So who is who?
Never seen this guy discussed in another book. He's probably not mentioned because other authors don't want to have to deal with his metallic asparagus guys. Makes the whole field sound idiotic. However, these guys saved Reagan (if the story is true - he remembered it without being hypnotized first, which makes it more valid), so maybe the good guys are sentient space vegetables. Can the outer space veggies defeat the combined powers of the MIB/demons/space brothers? Stay tuned! Hey vegans, you're eating our allies, dammit!
p66 - Project X - investigate base in Antarctica cuz a lot of sightings close by in Oz & NZ.
p70 - Bender is visited again by the stinky blue-light guys, in a sort of out-of-body experience. "We have a special assignment and must not be disturbed by your people." And "We are among you and know your every move, so please be advised we are here on your Earth."
Dream? Maybe. Maybe not. When he snaps out of it the radio is on again. The radio is always on, even though he hasn't previously turned it on. A clue. The sound waves from the radio affect something; interfere with other frequencies as in when they try to mat & demat? Cancel out some frequencies that make it easier for these guys to mat? ?
Who is who here? The easy answer is the guy is a nut case, but it doesn't seem like it. Appearances of disembodied entities have been documented in the hundreds throughout history; there's also been hundreds of fakes.
That sulfur smell... I smelled it once. Uh-oh... Where/when was that? Hmm.... Oh yeah when I opened the fridge the other day.
Sulfur smell to author very real, convinced him events were real.
p73 - Author's 2 cohorts he confided in refuse to believe his demon-like story; even back then these visitants
must be ET's from another planet, no other explanation is possible. The groundwork was laid by all the cruddy space opera sci-fi in the 30's & 40's. The introduction of all of this sci-fi stuff into publishing must be part of the plot then. If there really is a plot...
This all happened on Contact Day when they were supposed to be trying to telepathically reach the saucer people with a canned message of peace. His write-up of the event, which he sealed & filed, disappeared from his file cabinet, with lingering odor of sulfur.
p74 - After 2 week vacation he comes home & gets visit from 3 men who materialize inside his room; same blue lights, ice cold, sulfur smell. So the MIB's are the same as the stinky demons I guess; at least these ones are.
The password for him to contact them again is "Kazik." They use the radio frequency as "a method of getting back to their base." Whatever that means... Hmm...
p81 - Another visitor with more info. The universe revolves around a central creator core. Different parts (astral planes or whatever) rotate at different speeds; they've just revolved into nearness to us. They're taking something from our ocean water, some element they need. Speedily, while they have time, before they rotate away. Hmm... A lot of plastic in our oceans nowadays, maybe now they wouldn't want it! Hah.
Marauders from another system will soon reappear in our vicinity. Last time they destroyed a great civilization near us. Planet where the asteroid belt is? Nope, later they say it was Mars..
The blackness/void to which they sent ships that never returned, would this be beyond the infrared (or UV rather) then, where you'd get less & less dense, atoms would be farther & farther apart until eventually you'd reach nothingness, or a point of no return...
p90 - They take him to their base in Antarctica, tunneled under the ice. No wonder they interfered after Project X was announced. Assuming any of this is true...
p102 - Exalted One answers questions. He says peeps live underground & come to the surface to take stuff & can make themselves invisible. Hmm, sounds too much like Shaver's deros. Too convenient an explanation for ghosts. Author would have been familiar with Shaver Mystery; at end of book he disagrees with this explanation for ghosts.
Their Leader says humans have been taken to their world as museum pieces etc, so these guys are not sympathetic to us. However he also says the humans did not survive; which corroborates another reference in another book (Barker's maybe) about the medium in this time (early 50's) who says "you couldn't survive there."
p115 - Author sees monster similar to Flatwoods Monster & faints. Same odor & icy hand. Is the Flatwoods Monster the "metallic asparagus" seen by Fred Reagan?
Hmm, just as I'm reading this section, I smelled that odor! Uh oh again... oh wait, I think either Mikey or Homer farted. It wasn't me; the dog did it!
p128 - Author is visited again, taken to the base, where 3 beautiful women anoint him with oil. This anointing is one of the common contact features pointed out by Keel; which could have a hallucinatory effect, depending on what the oil is. Did they do this to the author earlier as well? & he didn't mention it, or forgot about it, or got it mixed up & in the wrong place in the narrative? Anyhow this leads to the possibility that this entire thing is a confabulation; a fake cooked up by... who? The CIA again; or whoever. Probably deeper than them. I don't believe this Antarctica base dealie.
p136 - Interesting theories from a Seattle correspondent, which turn into threats. Author could have gone to the FBI & tried to get the guy on blackmail, but doesn't state that he took any action. Nothing ever came of it.
p154 - "Angel hair" is a by-product of their processing our sea water. If so, hasn't this angel hair stuff kept falling since these guys supposedly left in 1960?
Very disturbing reading, if any of it is true (note: it probably isn't). Visitors could rotate into range at any time; the 15 year window of these particular guys might be taken as a baseline for a "danger" period from any one group. However, as I said earlier, shortcuts could be taken across the interior planes, which should rotate faster, like the inside of a turntable with the increasingly shorter grooves. Seems like they could come here whenever they want.
But why are the higher densities, the blue light areas, icy cold? & the slower moving infrared areas generating great heat. Seems like it should be the other way around; the greater movement generating the greater amount of friction. Oh well, stupefied as usual...