Hugh Hughes produced an excellent guide to railway locomotives in India called simply 'Indian Locomotives'. This was published as a four-volume set of books with 'limp' covers by The Continental Railway Circle.
Brief details of these volumes are given below:-
Part 1 - BROAD GAUGE 1851-1940: First published 1990 (ISBN 0 9503469 8 5)
Part 2 - METRE GAUGE 1872-1940: First published 1992 (ISBN 0 9503469 9 3)
Part 3 - NARROW GAUGE 1863-1940: First published 1994 (ISBN 0 9521655 0 3)
Part 4 - 1941- 1990: First published 1996 (ISBN 0 9521655 1 1)
This comprehensive work gives dimensions, statistics and includes industrial locomotives. Part 2 includes Burma, part 3 includes minor railways in Burma and part 4 has sections on Bangladesh, Burma, Pakistan and Sri Lanka. All-in-all, an essential reference.
These books are available directly from The Continental Railway Circle. For further information go to their internet site here.
My own, rather modest, exploits to see Indian Locomotives on my three visits to India are outlined in a post here.