I've always been fascinated with marine biology, and I was pleasantly surprised when I recently learned of a book that has just come out, Poseidon's Steed by author and marine biologist Helen Scales. (You can check out the book on Amazon right here.)
I'm about three chapters into the book at this point, and have to say that this is a fabulous, fascinating read on the subject of the reality and the mythology of seahorses by an expert in the field. What is so neat about the book is the readability and accessibility of the book. You can actually read an in-depth review of the book here, on the National Greographic website. The review even has some neat video of seahorses and stuff!
Excellent read so far, highly recommended.