I read it because I was going to be seeing it performed. It was helpful toward understanding the performance. 
 The short version: Richard needs to kill everyone in the way of his being crowned king. To that end, he acts kindly to them, then has them killed. Even his most loyal accomplice realized he is out of favor and tries to get away, but is caught. 
 It is called a tragedy, and one is supposed to identify with the hero's rise and fall. I could only cheer the fall. 
 One especially effective scene (to read and to see) is the night before battle when the spirits of all who have been murdered appear both to Richard (Despair and die, they say) and to Richmond, whom they encourage.