The Rough Guide to Rajasthan, Delhi and Agra is the most comprehensive guide available. From the magnificent Taj Mahal to craft shopping in Rajasthan, the inspiring full-colour section introduces all the regions highlights. You’ll find detailed accounts of every major tourist sight, along with critical reviews of all the best places to sleep, eat, drink and shop, in all price ranges. There’s comprehensive detail on getting around by train, bus and car, while the guide also includes clear and comprehensive maps of all major towns and tourist sites in the region. The full colour introductions and inserts, along with inspirational photography, give you a flavour of this region’s unique cultural heritage. All the practical advice you need before you go and when you arrive, complete with expert coverage of the regions history, religion, wildlife and language. The Rough Guide to Rajasthan, Delhi and Agra is like having a local friend plan your trip.
I'm pretty partial to the Rough Guides. They're a little skimpy on reviews of hotels and restaurants, but have tons of description and background about sights, history, and culture. Rough Guide India is about 3 years old, so I was excited to discover that they put out this regional guide just last year. Will probably combine this with Lonely Planet India.
As always, you have to account for that the fact that prices rise every year. And as always, the Rough Guide doesn't list exact prices for hotels, but instead just puts each into a price bracket. *sigh* Still it's an excellent companion and I'm glad I took it with me.