Travel Guide Books
This website is just a basic introduction to the Philippines and you may want to read up more!
I can thoroughly recommend the 'Philippines Travel Guide' by Jens Peters. This Author previously wrote the Lonely Planet Guide, but this book is widely considered to surpass the Lonely Planet Guide. Loads and loads of information and probably the only guide you need! For more pictures and perhaps easier reading I can also thoroughly recommend the 'Globetrotter Island Guide - Philippines' by Lindsay Bennett.
You can view a huge selection of Philippine travel books at Amazon.com:
For your travels you may want to order an underwater camera. You really use them in the Philippines and the price has come down a lot!
You can even order snorkeling gear at Amazon. You can often hire snorkeling gear in the Philippines but it is always nicer and better to have your own!