walking among us - david jacobs
Jacobs is an old-school ufologist, he goes around interviewing people and has been for decades seeing what matches and what doesn't in abduction stories. His theory on what abductions are is basically a hybridization program that insectalins(aliens that look like insects) are doing and that most of the aliens descriptions we see exist because they have a caste system.(i.e reptilians abov grays above human hybrids) etc. And that slowly but surely they're placing these hybrids into the world slowly taking over. If nothing else he at least can claim that there's thousands of abductees he's interviewed. he has an older book hidden threat or something liek that but i haven't read.
As a sidenote, Buzzfeed, of all places, actually did a neat little interview with a supposed alien abductee and had jacobs explain a bit about the phenomena. No judgment(other than the comments) and whether the guy was saying the truth who knows but it was interesting.