William Taubman spent 20 years researching Khrushchev: The Man and His Era. It seems a marvel to me how all that effort, sustained over so many years, now weighs so lightly on my hands!
Taubman is clearly an unsympathetic biographer. He gives his subject credit where it's due, but doesn't hesitate to be critical where necessary (which is most of the time). It's clear that Khrushchev was no moral exemplar, no great strategist or thinker -- not even a good father. As a national leader, he was a blunderer. The more he tried to show how capable or strong he was, the less people thought of him.