What's the best book to read if I want to understand why India and Pakistan separated after independence?

GQ. I’d like to know (and try to understand) this too.

I read a wonderful biography of Mahatma Gandhi, which went into detail of how that split happened, and what Gandhi was prepared to do to prevent it. I think the name of the book was The Life and Death Of Mahatma Gandhi, but Google gives me the wrong author, I think. I will try to find mine.

Not a book and not an overview, but this(1998_film) was a film that gave me a better idea of what happened in Lahore post-partition. It details the effect on a group of differently faithed young people after Pakistan and India are split and is very enlightening. One thing I have read elsewhere is that when Britain was leaving India, they just drew an arbitrary line down the country and that is why Kashmir is still in dispute.

Another work of fiction that is helpful is a novel called The Hindi-Bindhi Club which is a novel of mothers and daughters similar to The Joy Luck Club. It also gives a graphic description of some of the atrocities that were committed by both religious groups.

There’s a pretty decent description on Wikipedia
At the end of it there are also selected readings. I’ll try and go through my library and see what else I may be able to recommend.
@janbb actually the case re Kashmir was that basically the majority Muslim States of pre-partition India became Pakistan and and the majority Hindu States became India. Kashmir was a majority Muslim State, however the ruler of Kashmir was Hindu, and at the last minute chose to secede to India, causing the population of Kashmir to revolt. It’s a struggle the Kashmiri people are fighting to this day.