The following book treats the topics which are covered in the olympiads and also is a rich source of problems; (highly recommended)
The books listed below form the recommended reading for the various math competitions. Some are elementary, and some are not so elementary. As far as possible there are indicators to the type of the book but, of course, these can only be indicators....

Orders for the books can also be placed at SARASWATI PUSTAKALAYA, 138/1 GOPAL LAL THAKUR ROAD, Kolkata 700 108. Tel: 2577-1415.