I can't help but look at a Hawaii visitor guide and check out whether my favorite eateries, locations, and activities are included. This one has a lot, but it covers all the Hawaiian Islands that visitors may, well, visit! That's a lot of material for one book to cover if its intent is to be complete. There are island-specific books that give more info (for example, the "revealed" series), but this one is darn good. It certainly focuses more on the activities for the low budget traveler than most do.
I know Oahu better than the other islands, so how accurate is Lonely Planet's Hawaii? It's pretty good. There are so many eateries in Honolulu than many are not included. Maybe it's good that you will be steered away from my favorites! Seriously, I like The Shack in Hawaii Kai, Island Manapua in Manoa, and Volcano Joe's Island Bistro across from the UH campus for some delightful vegetarian [EDIT: Volcano Joe's is no more...]. There's the Xcel outlet store in Haleiva, BBQ in Wahiawa, super diving off Makaha, and a less exploited trail and waterfall in Lyon Arboretum, right next to the heavily-used Manoa Falls trail.
There were some favorites included. Willows is a buffet treat in Makiki, Deep Ecology in Haleiwa is a very pleasant and knowledgeable dive shop, and the Honolulu Zoo, although okay as zoos go, has its Wildest Show in Town summer music series every week (only a $2 donation requested... cheapest deal in Waikiki).
This isn't a bad choice for a guide book if you are only going to take one book. Nothing beats asking a local, however. Be friendly, and show aloha to the residents and to our special places. Don't litter, and pass a site by if it looks too crowded. There are plenty of things to see and do.