I've read The Tibetan Book of the Dead and In Search of the Miraculous...both highly recommended.
The TBotD gives a fairly accurate(yet generalized) map of the territory one may encounter during entheogenic journeys. Along with some advice for steering oneself towards peak experiences and away from dark or base experiences. It is a book every psychonaut should have in my opinion. It was created by Timothy Leary and his boys in the early days of LSD research in the 1960's. I've found that I rarely think about the book until I'm within a trip and I need its advice. More than a few times remembering its message pushed me right back into the light before I spun out.
In Search of the Miraculous is a great summary of Gurdjieff's teachings from his pupil Ouspensky. It got me into Gurdjieff and gave me alot to think about. Although, when I've met students of Gurdjieff they say it pales in comparison to the teachings Gurdjieff wrote himself.( such as
Beelzebub's Tales to His Grandson) But I have heard his books are purposely dense, contrived, and esoteric, so, Ouspensky's summary is a great way to jump in and begin blowing your mind with some summaries of the teachings right now.
As far as meditation books go I'm a huge fan of
Undoing Yourself with Energized Meditation by Christopher Hyatt. This book is highly entertaining and makes one rethink their reality while also giving an extremely easy to follow and effective meditation method devised by Hyatt through researching and combining various meditation and yogic practices into one method that is easy to understand and practice for a modern person from the Western Hemisphere. Check it out...whole book for FREE!
Undoing YourselfIn the province of the mind what one believes to be true, either is true or becomes true within certain limits. These limits are to be found experimentally and experientially. When so found these limits turn out to be further beliefs to be transcended. In the province of the mind there are no limits. However, in the province of the body there are definite limits not to be transcended.-J.C. Lilly
The Spice must flow
Zat was Zen and dis is Dao.