The History of Recreational Sport-Fishing
The first book I read again and again as a kid was called Dictionary of Fishes by Rube Allyn. It had both freshwater and saltwater fish in it, with full descriptions of the many different species. When I was 20, my favorite book was Billfish by Charles Mathers. It had information on how to catch all the billfish of the world, as well as where to catch them and the best time of year, and it had lots of photos too. I was hooked.