Here is a thread of suggested books, from the main page:
http://www.3fatchicks.com/forum/showthread.php?t=49308
I never purchased a med. diet cookbook, but I've found enough recipes here and elsewhere on the web that I didn't need to purchase a book.
You said this is a lot different than how you usually cook ... just curious, how is it different? I found that it was quite similar to how I cooked, so it was a pretty easy transition. I already ate a lot of fresh fruits and vegetables, but I had to get used to incorporating seafood and more vegetarian meals. I'm far from religiously following this, but this is ultimately the way of cooking that I strive for.