He explains all the basic principles of pulse and rhythm and how this can be found in rhythms all over the world. This is one of the best books to start with if you want to study rhythm but I also highly recomend it to all musicians (I had been playing the piano for many years when I read it and it tought me a lot).
You should also check out Flatischlers great drum band "Megadrum", it includes one of the greatest percussionist on this planet, excellent stuff.
Three other recomended rhythm books "The healing drum" "The drummers path" and "A Rhythmic vocabulary".