It's the only book worth considering if you're a remotely-serious birder. If you want to cut down on size/weight and on number of out-of-range species to sift through, and if you don't mind buying more than one book to cover multiple trips, consider one of the regional derivatives: Search Results: Bloomsbury Publishing (US)feedback on bird guide for India (or region). Richart Grimmett
But the all-subcontinent original is portable enough.