Well, for starters: there's no index. How did that slip through the cracks? Since the functions are grouped by type, you need to know what the function is before you can look up what it is, or just flip through 114 pages scanning for it, which leads to problem number 2: the typography is such that the function names blend right into the text.
The function reference identifies what is returned by the functions by data type (e.g., integer), but not whether it's a pointer to an array or just a number, or what. The Leon Atkinson book, otherwise even lamer than this book, at least got that part right.
Advice to O'Reilly: give up on the pretense of always having the "preeminent expert" write your books. Get professional technical writers, partner them with the big name "creators" of the technology, and the quality and timeliness of the books will improve. Thank god Larry Wall didn't write the Perl book. O'Reilly doesn't have the field all to itself anymore, so they shouldn't be resting on their laurels.