We go every year, been to kauai, Oahu, Lanai, Maui and Hawaii (The Big Island).
For a first timer/honeymooner, I would also suggest Maui. The snorkeling is great, restaurants of every type adn plenty to do away from the beach.
Here is my generalization of each:
Kauai - Very slow, laid back, sometimes difficult to find places to eat, not a whole lot to do other then relax, but very beautiful and not at all commercial.
Oahu - Honolulu and people, but you can find quiet areas. Just not my favorite or even in the top three for vacation.
Lanai - Even slower than Kauai, great day trip, but that's about it for me.
Maui - Whatever you want, it's here, like I said above. I also suggest the south side (Kihei/Wailea/Makena), but try to get out and see the whole island. Do not bother trying to drive around the northwest side of all the way around from Hana, waste of time, IMO. Speaking of Hana, if you have not done it before, do it once.
The Big Island - Definitely stay on the west coast/Kona side. The bid resorts are here, but so are the beaches. It's a bit more laid back than Maui, especially as you get away from Kona, but not as much as Kauai. It and Maui are my favorites. Great snorkelling at either. The Volcano is really something and plan to try and stay at the observation area until dark. Do the park/crater during the day and drive down (get dinner on the way) to the observation area about an hour before sunset.
Anyway, best books I have found are the one's the sell at
www.wizardpub.com, written by Hawaii residents. You can find them at most major bookstores. They are generally blue with an aerial pic of the island on the cover and titles like The Ultimate Maui Guidebook. They will show you every beach, tell you about the services at that beach and show you which side of the beach has the best snorkelling.
I was in Maui and Hawaii this past August. While snorkelling just off the beach from our hotel (The Grand Wailea), I saw octopi, eels galore, triggers, great coral and then had a nice size 10'-12' Manta Ray swim about 10' right under me, coolest thing I have ever seen. I knew they were out there though since people had seen four of them earlier in the day. You could actually see them from the beach.
Have fun and try to get out of your room. I realize it's your honeymoon, but Hawaii is awesome.