I havent gotten far into this book but it brings up some good points.
At the same time i remember reading somewhere (spirit molecule?) of some experiment being done where a person was given a complex math equation far outside their ability and then given some DMT, the person asked the entities to solve the equation and they did correctly. Now maybe DMT accesses some part of the sub conscious that is really good at math, which can also access other information stored by the unconscious, who can say but it is interesting. It should also be kept in mind that other people in the world may of done experiments which were not legal and so not published in some scientific journal or written about anywhere, in fact i am willing to bet the craziest trips go unreported regularly. The question of whether or not psychedelics can give a person new information is an important one, but i think its important not to be to sure of either perspective, especially while doing an experiment.
Another experiment with psychedelics to determine whether or not the "spirits" exist outside the mind was done by this guy
http://www.pot.tv/archive/shows/pottvshowse-1781.html some of you may of heard of him if you are into ethnobotany his name is Chris Bennett. The relevant part starts at just around 13 min into the video. (theres lots of interesting videos on that site, i suggest other burning shiva vids, some much more proffessional then this particular one) He asks questions in what he calls "the wheel of anthropos" a circle of people and each person (all of them on shrooms) can only say one word to answer it, none of them know before hand what will be asked, some of it very obscure questions, as the circle goes around an answer is gained which is intersting, i suggest you watch.
Who can say what will really prove whether or not psychedelics provide information from outside the individual mind, if you believe as many ancient psychedelic religions do that reality is all a product of the mind then its kind of a moot question. This may sound crazy but then you should remember that none of us actually experience reality, we experience our consciousness of what we call reality, there is a big difference. If DMT is a major factor in creating consciousness then it really brings up all kinds of other questions as well.
That said the book is interesting and needed to be written, lets just hope lots more scientific testing is done, but lets try and do some experiments ourselves.