Alison Weir has made a good career of writing about the Tudor reign, and this book is one her better ones. She managed to get her hands on good source material written by contemporary historians who had first-hand access to the events in question.
In The Making of the Tudor Dynasty the authors devote all of two sentences to the murders of King Edward V and his younger brother Richard, while this book is devoted to the events leading up to and after the murders.
I am always amazed, with histories like these, at how much material there is for researchers to use. These events happened centuries ago, yet there are documents still in existence that give amazing detail as to what was going on.
Weir's ultimate conclusion, based on all the evidence she found, is that Richard III really did have his nephews murdered to secure his seizure of the throne of England - don't worry, I didn't just spoil the ending for you.
Still, even though the conclusion is a forgone one, it's still a gripping book. Weir knows how to write a good story.