We have been big fans of Eyewitness as it is not only a guidebook but almost a souvenir as well. However, the more we travel the less attracted we get to these books. They are definitely beautiful and visually informative. You get excited to see some of the places because of the pictures, diagrams and maps. The problem is that the information for each place is very poor, you don't get more than a couple of small paragraph per place.
Also, and more importantly this guide misses some interesting sights in Delhi. We visited India with the excuse of attending the wedding of a friend, so we were constantly surrounded by locals who were always surprise why places like Chattarpur or Akshardham were not even mentioned in the guide. I invite you to google this temples, I am sure you will agree that such wonders are unmissable in any serious guidebook.
India, and particularly the places covered in this book, are so rich in history that you shouldn't miss any information in each place you will visit. You are investing in going far away and reaching these monuments: make sure that you have a proper guidebook in hand. You will find information written by the monuments and maybe you will hire a guide but if you are taking the time to read this review is because you actually care for the contents of a guidebook and because you like to read ahead, plan and review while you are wandering about in these heritage places.
Enjoy your trip to Incredible India!