I've learned to scroll down and check the number of pages on Amazon. Also often check the size (after getting a paperback that was ridiculously small).

I have a few quilting books but I bought them all used or in lots on ebay. I find the most helpful quilting info is usually online but I have purchased a few patterns that were too difficult to recreate on my own.

The books that I have found to be the most helpful included lots of step by step up-close pictures and examples of ways to vary the blocks for different looks.