As already said, the Sea of Cortez is not the place for sharks anymore. It's still a nice place to dive, and one of the best for sealions, but the sharks are all but gone.
I'd also go for the Shark Watchers Handbook. It's a bit out of date, and you'll probably get second-hand only, but I still use it as a reference. It has basic ID info, but great info on where to find the sharks. Just remember it was written a few years ago, and the shark numbers have dropped rapidly everywhere.
I suspect every self-respecting taiwanese shark finning vessel bought this book as soon as it was published.
David