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There are quite a few books out there.
It's been the general concensus that if you are a true beginner to AdWords then a book can be useful because the info is organized. I'm not sure that you'll find anything in it that you won't find in this board, however, the fact its in one place, makes it a good starting resource.
However, you need to know the AdWords CP as most books aren't updated often enough compared to how quickly G updates features. This can leave you with a false sense of security about what you know.
If you know a bit about AdWords, and aren't a beginner, then these boards will give you more current info and trends than a book (especially a print one).
Don't forget to check out the Library [webmasterworld.com] as well.
Hope that answers your question.