I am heading off to the India next month to travelling from Mumbai up to Delhi and Rajasthan and thus was looking for a good guide book! I've had the Lonely Planet - India guide for several weeks and it appears excellent and concise and is highly recommended by everyone I speak to. I was also looking for a more specific regional and city guide and thus when I saw this book I thought it would be ideal! However, when it arrived it is simply just the Rajasthan, Delhi and Agra pages lifted from the Lonely Planet - India book! Therefore if you own that, this book is of no use!!
At the same time I ordered the Lonely Planet "Best of Mumbai" and it appears to be an excellent, colourful guide with useful maps. By chance this week I popped into a book shop and found the "DK Eyewitness Travel Guide" to Delhi, Agra and Jaipur and bought it! It is an excellent regional guide and is exactly what I was looking for from the lonely planet guide, I would highly recommend it!
In summary, if you have the lonely planet India guide, do not buy this book as you already have all of the information it contains. Secondly, although the information is very useful, I would also suggest buying the DK eyewitness guide as an adjunct, simply for the excellent maps and pictures to help visualise the places you will be going!