Here are a few highlights from my collection:
- They Knew Too Much About Flying Saucers by Gray Barker, Second Edition, signed by the author (1956)
- Invisible Residents by Ivan T. Sanderson, First Edition (1970)
- Book of Great Jungles by Ivan T. Sanderson, First Edition (1965)
- The Flying Saucers Are Real by Donald Keyhoe, First Edition Paperback (1950)
- Man, Myth, and Magic, all 24 volumes, (1970)
- Practical Zoölogy by Alvin Davison, Ph.D. (1906)
The last one isn't about unexplained phenomena but it is still the oldest book I own and a testament as to how far zoology has come since 1906.