I recently read a new edition of The Edge Of Reality (Newburyport, Massachusetts: MUFON, 2023). It originally came out in 1975. It's largely a record of some discussions about UFOs between two of the foremost researchers in the field, J. Allen Hynek and Jacques Vallee. I didn't read the 1975 version, and I don't know how different the update is. I think it's the same or almost the same aside from a new foreword (by Hynek's son) and a new introduction (by Vallee). The bulk of it doesn't discuss the developments of the last half century, since it was published so long ago, but it has a lot of relevance and significance anyway. I still think the best overall introduction to the topic that I've read is Leslie Kean's UFOs: Generals, Pilots, And Government Officials Go On The Record (New York: Three Rivers Press, 2010). The Edge Of Reality is a good supplement to Kean's book. It addresses a lot of issues not covered or not covered as much by Kean, like issues of interpretation and the history of research. And it's written by two giants in the field whose experience and inside knowledge are more significant than Kean's. Hynek has a lot to say about his experiences with the United States' government's incompetence and corruption in handling UFO issues, for example. The book covers a wide range of subjects related to UFOs, though their comments are often brief. Vallee (rightly) rejected the extraterrestrial explanation for UFOs, and Hynek seems to me to have leaned in that direction as well. He gives some attention to views like mine, that UFOs are produced by human paranormal activity. He even draws a comparison to poltergeists at times, as I have. Neither Hynek nor Vallee goes into as much depth as I'd like about these issues, but there's a lot that's helpful in what they do say.
Another book by Vallee, Dimensions (San Antonio, Texas: Anomalist Books, 2008), opens with a dedication to his friend:
This book is dedicated to the memory of Dr. J. Allen Hynek.
As a scientist, he was the first to grasp the significance of the problem. As a thinker, he understood its relationship to other deep mysteries that surround us. As a teacher, he shared freely his data and his insights.
As a man, he wondered.