You can't get much more villainous than the stuff of history described in this book. Author Matthew White takes us in historical order through the hundred most horrific events in human history, as estimated by him based on the bodycounts and rationales of more orthodox historians. Occasionally he gives us small digressions in the form of essays on such topics as genocide. The writing is clear, rather journalistic, with a certain kind of wincing humour that doesn't prevent him from getting into reflections about the sheer awfulness of it all.
Much of this may be familiar to you - quite a bit of it is to me - but it's (morbidly) fascinating, and certainly illuminating, to see it all in one place, with the likely facts and historical interpretations filtered through a single sensibility, that of a person who clearly knows this stuff backwards.