if you are looking for info on hobbyist care, the book is not gonna be worth it (it only has basic care info). BUT the book is quite rich in diagnostic info and a decent amount of scientific info where applicable, includes lots of nice pics of live specimens, also some museum specimens. For each species/subspecies, there are info on material the author examined (live and museum specimens and the location of collection, size etc), some general info on the fish (ex. distribution etc) and diagnostic info. Granted many (loosely speaking lol) people don't agree with everything the author wrote (eg. all the subspecies have been raised to species level), and there are things i don't quite agree with (eg. ID of P.bichir), i still enjoy the book a lot. the best features IMO are the pics and the diagnostic info. So it's worth it if this is what you are looking for....
btw i got mine for about $80 when it first came out.