The maps are better than what most Indians have ever seen in their lives, which is exactly why travellers don't need it. If you are taking public transport around the country, you get plenty of information about how to go where from LP India or from information at train stations, bus stations and other travellers. It simply isn't worth the excess weight (in a rucksack). If on the other hand you are cycling or have your own motorized vehicle, this would be irreplacable (so be careful who you show it to).
While working on an on-going university research project I have spent five years driving the back roads of India. This book has saved my sanity as well as my tires and axles. It is by far and away the most helpful road atlas available.