"Hindi, Urdu and Bengali phrasebook" by Lonely Planet is really very helpful.
It is very informative, well organised, cheap and pocket size 304 page phrasebook for three big Indian languages - Hindi, Urdu and Bengali.
The great thing about this phrasebook is that it is very well organised and has easy to follow content page in the beginning.
There are scripts explained of every language and the phrases are in original script and English transliteration.
Hindi and Urdu - two sister languages are in one part of the phrasebook and Bengali makes another part.
Every part is devided into:
TOOLS(Script, pronunciation, grammar and basic vocabulary such as numbers and days of the week etc)
PRACTICAL (involves transport, directions, border crossing, accomodation, shopping, communications, money and banking, sightseeing, business, specific needs)
SOCIAL (meeting people, interests, feelings and opinions, going out, beliefs and cultural differences, outdoors)\
FOOD (eating out, self catering, vegetarian and special meals, culinary reader)
SAFE TRAVEL ( emergencies and health)
DICTIONARIES (English - Hindi/Urdu and Hindi - English and Urdu - English)
The Bengali part of the phrasebook is analogical to Hindi/Urdu part.
The book has emergency and important phrases written on the inside part of its cover, it has small maps on its pages to show where the languages are spoken.
I haven't used the Bengali part yet but I think that Hindi and Urdu phrases written side by side (Hindi in Devanagari script and Urdu in Persian script) can be a bit confusing so it can take time to get used to it.
However I would agree that Lonely Planet is the best phrasebook brand you could possibly find and I think that's correct because these phrasebooks are of a rather good quality. I still use my Hindi phrasebook to learn the basic phrases in different life situations (we are still in India). I would definitely recommend it but, of course, it's only a phrasebook and we shouldn't expect a full language course from it. For that purpose, I would recommend Hindi books by Rupert Snell.