ISO: The Quintessential Floridian Cookbook
Used to live in Orlando, and traveled to Tampa/St. Pete quite a lot. The only truly local cookbook that I ever saw was "The Gasparilla Cookbook." I think it's published by the Junior League of Tampa, which is, coincidentally, where I would first point anyone looking for recipes representing a particular city that doesn't have a well-defined food scene (like NYC or New Orleans). Also, I believe the Columbian (a very popular local restaurant in nearby Ybor City) has published a book as well - while I can attest to their food being quite good, I can't attest to the cookbook itself.
Try this link:
For Miami, you might try the "Three Guys from Miami" books - although mostly Cuban-American takes on traditional Cuban cuisine - it's a bit limited in scope (Miami has a lot of different cultures like any big city), but the recipes are all very good, although I do think the book is a bit hokey. You could probably find a better cookbook, but I don't know of one (I always drove right past Miami in a hurry to get to Key West).
As for general "Floridian" books, I haven't seen anything promising in particular, but I do recommend anything by Norman Van Aiken. Floridians claim him as their own (his style is called "Floribbean") - and his recipes always remind me of the natural cultural fusion that Floridian cuisine always seems to provide.