I've bought 3 editions of the Unofficial Guide to Disneyworld Florida, which is an incredibly informative, comprehensive and useful guide. However, I was disappointed in the Unofficial Guide to California with Kids, which lacks the (sometimes excessive) detail, the humour, and the mix of enthusiasm and criticism that makes the DW Florida guide such a gem.
For a start, California with Kids doesn't cover Disneyland California properly - you have to pay out for a separate book about that. There's a map of the main park and a list of attractions but not important information like height restrictions. There's very little about the second park (CA Adventure). Much of the little it does include is given over to general chat - if they were restricted for space, I would have preferred some practical information. It did feel like they'd done this on purpose to make you buy the separate park guide. But then, there was similarly scant information about other parks like Knott's Berry Farm - not even enough to decide whether it would be worth a visit for my family.
Secondly, California is so big and varies so much within the state, it's very hard to cover in a single book - I'd hoped that by focussing on things to do with children, we might be able to single out some good places to visit and some useful tips. However, the coverage of each location and attraction is very superficial, and felt very uncritical. There is a lot of useful information, but I found it needed to be supplemented with more detail from other guides to the area.
My other criticism is with the page headings. The book is divided into geographical Parts, each subdivided into areas, but the page headings only show you which Part you're in, not which area. I found I was constantly flicking back and forth trying to work out where I was. There are maps, but they're all over the place, and it's hard to work out how they relate to each other if you're travelling.
The guide is chatty and readable, with bits of personal experience to keep it interesting, but it's so light on information, I felt this space could have been better used for some more detail about places and attractions.
This book needs to be a lot more detailed to be really useful, or to focus in on a smaller area and do it properly. The Lonely Planet Guide to LA & Southern CA (NOT the one for the whole of CA) is the most useful one I've found so far.