I read the pdf several years back. At that time, I must’ve had questions about and thoughts of learning more about Buddhist cosmology and came across the book.
I can’t say I have studied or know alot about Theravada orthodox teachings on Buddhist cosmology, but depending on what’s meant by “the accuracy of the book”, I believe it would / should? fall in line mostly with Theravada orthodox teachings. Included in the title of the book, “according to Theravada and Sarvsativada sources”.
Based on my understanding at that time and currently, I can’t say how accurate all the things mentioned in the book are, but I believe it should be accurate enough that it can help one to get the general idea about the topic and the different subjects. I mostly read quickly through the book, but I do believe the book gathers Theravada teachings and sources on the subjects in one book.
If one does read it, my advice is to use one’s discernment and decide on what to take in and discard or use or not use from the book. I believe the materials in the book can possibly be used to cross reference, compared, and additional information about the different realms and beings.
But in my opinion, the material’s in the book are not the most important area / dhamma teachings to focus on.
One part of the book that did drew my interest or I was most interested in (focused) was the part about devolution of humans and the future of humanity, which is the agganna sutta. Puredhamma also has a post and materials on that sutta.
By comparing and relating the two materials mentioned, as well Venerable Waharaka Thero subtitled English desana on anicca. The experiences benefited my learning of “anicca khayatthena”.