You buy Cris Kohl books for the basic info on stuff. He is very good at that and I would not hesitate to buy another of his books. I own several. The more you dive and get "connected" you'll find ways to get accurate numbers from local sources. It's always best if you can find someone who dives something your interested in. Besides numbers they will usually share a lot of little details about the wreck site in question making your dives that much more interesting.