I recently bought this book after purchasing a few Lophophora specimens, and was somewhat dissappointed. Much of the information is sparse or inaccurate, and overall you come away having learned little. It is vague in describing the effects and chemistry of the plant, and minimal effort is made to try and describe different species and varieties.
A much better book to buy would be "Peyote: The Divine Cactus", by Edward F. Anderson. It gives a detailed ethnographic history of peyote, describing the modern ceremonies of the Navajo, Plains, Huichol, and many other Indian Tribes. He studies its effects on humans in detail, its chemistry, legal aspects of peyote, and (most importantly!) the botany of Peyote, giving a comprehensive view of the species as well as its different taxonomic varieties (eg. L. williamsi, L. diffusa, L. jourdania, L. fricii, L. decipiens, etc.). Much of the information contained within cannot be found on the internet.
Although most of Gottlieb's material is dealt with in Anderson's book, nevertheless the practical information on grafting and mescaline extration is much more detailed in Gottlieb's (probably because of the different target audiences :-)
All in all, still good to have as an accompaniment.