It is above average for a fish book, and reasonably comprehensive (the diseases section is very good), but there are still mistakes in it. I think they still name the wrong species of bacteria that grow in our tanks, for instance (even though the correct species had been known for at least 4 years before the book was published). But, all in all, it is pretty good. There are some better ones out there, but it is an excellent 1st book if someone didn't have this information already.