This is Lonely Planet's omnibus guide to Mexico, the whole enchilada, you might say. They've managed to do a very decent job of it. There are few photos, compared to other guides but there are dozens of maps and the ones I used were all of good quality. I've used it to plan trips to Hutulco and Zihuatanejo and in each case found it had covered off the major attractions well. For accommodations it focuses on boutique or small to mid sized family-run hotels, pretty much ignoring chains or big resorts (which it describes as "hulking"). Usually provides a good range of restaurants, in terms of cuisine and budget, but as these come and go quickly, you can count on a few being gone by the time you get there. Because it covers so much ground, the sections of the guide on history, culture, food are short, but still cover the basics. It has a casual and easy to follow style
Lonely Planet publishes smaller, regional guides that go into more details for specific destinations but if you're looking for an overview of the country in one package, I'd reccomend this one.