I assume you are mostly interested in the soldiers rather than their families. There are dozens of books which detail the personal accounts of soldiers who served in India in the late nineteenth century, but for a broader picture you might be better starting with some of the twentieth and twentyfirst century academic works on the subject as they tend to draw on sources over a wider geographical area and time span than the personal anecdotes and biographies. An example of the former might be From Recruit to Staff Sergeant by NW Bancroft (1885 Calcutta) republished by Ian Henry Publications in 1979. Many of the first hand accounts were written by officers, and fairly senior ones at that, so they may lack the soldier's point of view. For an excellent example of the second type, an academic study of the period, try Sahib by the late Richard Holmes (of Military Rides fame). His book has a comprehensive bibliography and detailed notes on sources which should allow you to follow up on anything which you find relevant.
And don't forget the museum and regimental association for the successors to the 2nd Dragoon Guards. They may well be able to provide other unpublished accounts of the life of a trooper at that time. There is also a Facebook group.
The Queen's Bays' first stay in India (1857 - 1875) would have been much busier than their second posting there 1885 - 1894. You don't mention your ancestor's dates but it is quite likely that he wouldn't have been with his regiment for both those deployments to India.
Thanks for that. He served during the second posting and had, I presume, an extremely quiet time of it. That's what got me thinking about just what his life consisted of. I know that it was, generally, discouraged for soldiers to spend any time outside of the cantonment so it must have been seven years of pretty dull routine. Perhaps that's why he spent so much time in the hospital!