Beatles fan....Does this info seem accurate?

Ok so i got this info from Youtube. i'm not sure where this info came from, but does it seem legit?


http://www.youtube.com/watch?v=8CMdqWh_J8I

John Lennon wrote the song in January 1966, closely adapted from the book The Psychedelic Experience by Timothy Leary, Richard Alpert, and Ralph Metzner, which they based on, and quoted from, the Tibetan Book of the Dead, with the understanding that the "ego death" experienced under the influence of LSD and other psychedelic drugs is essentially similar to the dying process and requires similar guidance.
Peter Brown claimed that Lennon's only source of inspiration for the song came from the Tibetan Book of the Dead, which it says Lennon read whilst tripping on LSD. George Harrison later stated that the idea for the lyrics came from Leary, Alpert, and Metzner's book. McCartney confirmed this by stating that he and Lennon once visited the newly opened Indica bookshop—as Lennon was looking for a copy of The Portable Nietzsche—and Lennon found a copy of The Psychedelic Experience, which quoted the lines: "When in doubt, relax, turn off your mind, float downstream". Lennon bought the book, went home, took LSD, and followed the instructions exactly as stated in the book.