Derbrucer,
Bert Fields' book, ROYAL BLOOD, is frequently is a direct refutation to Alison Weir's book, which I also have. I not heard great things about Weir as a historian and what I've read of her book does not convince me. Fields dismantles her arguments with lawyerly-like precision.
Of course, the still definitive book on Richard III is Paul Murray Kendall's great biography from 1955.
There is really nothing in Richard's character, loyalty, and what is known of his actions while serving under his brother, Edward IV, that would lead one to believe he would kill his much-loved brother's children. And there's really nothing in his subsequent actions after the supposed murders that he would. Even Edward's widow put the rest of her children in Richard's care. Hardly likely if he murdered her boys.