The Book is better.. If I remember correctly they used injection on the 400 case studies. The results are different than smoking I heard. Smoking it or drinking it orally (Ayahuasca) has better effects.
Rick Strassman also has another book out titled
"Inner Paths to Outer Space" (regarding DMT) that is better than that one. And it is more up to date.
http://www.rickstrassman.com/ Product Description
An investigation into experiences of other realms of existence and contact with otherworldly beings
• Examines how contact with alien life-forms can be obtained through the “inner space” dimensions of our minds
• Presents evidence that other worlds experienced through consciousness-altering technologies are often as real as those perceived with our five senses
• Correlates science fiction’s imaginal realms with psychedelic research
For thousands of years, voyagers of inner space--spiritual seekers, shamans, and psychoactive drug users--have returned from their inner imaginal travels reporting encounters with alien intelligences.
Inner Paths to Outer Space presents an innovative examination of how we can reach these other dimensions of existence and contact otherworldly beings.
Based on their more than 60 combined years of research into the function of the brain, the authors reveal how psychoactive substances such as DMT allow the brain to bypass our five basic senses to unlock a multidimensional realm of existence where otherworldly communication occurs.
They contend that our centuries-old search for alien life-forms has been misdirected and that the alien worlds reflected in visionary science fiction actually mirror the inner space world of our minds. The authors show that these “alien” worlds encountered through altered states of human awareness, either through the use of psychedelics or other methods, possess a sense of reality as great as, or greater than, those of the ordinary awareness perceived by our five senses.
EDIT-- Another excellent read on this subject is "Supernatural" by Graham Hancock.