I picked up this book from the library, coming to it as a then-newcomer to California. I read/browsed it, and my reaction is ... Meh. Decent book, nice illustrations, decent text, I learned a few things. But I would never *buy* it. Maybe it's trying to do too much in one book? I've browsed through many of the California Natural History Guides series, also published by UC, and find them more focused, and generally more interesting.
If you live in California, your public library will have a bunch of these guides. Try before you buy, is my recommendation. The book at hand is OK, but perhaps more suited to a YA audience. And a bit too PC for my taste. YMMV.