I read this in two sittings and was utterly blown away. It's by far the best book about the UFO/encounter experience I have read in a very long time (possibly since the original Communion). Strieber has clearly done a lot of deep thinking about his experiences over the years, and the book is grounded in an agnosticism that I find refreshing and candid. There are more questions than answers here, but it cuts closer to the root of the mystery than dozens of other books on the subject.
The introduction by Jeffrey Kripal, Chair of the Department of Religious Studies at Rice University, sets the perfect tone, correctly placing contemporary contact/encounter experiences like Strieber's among other historical mystical and transpersonal phenomena.
Fascinating and provocative and highly recommended.