HOwever, I would wait if I were you. The cert. agencies vary on certain details, & if you want to pass you tests, do not confuse yourself by absorbing a stew of resources right now. Wait until you have your OW tests done, then you will know more about what subjects you want to read more on.
There is one book that will entertain, inspire, & not bog you down in details: Scuba America by Al Tillman & Zale Parry (of Sea Hunt.) They relate the history of the sport in America with some humerous anecdotes & good visuals. Have fun!