The Norman Conquest: The Battle of Hastings and the Fall of Anglo-Saxon England by Marc Morris (nonfiction)

Exceptional history book with a fascinating narrative thread.  I like books that are obviously well-researched without being a list of facts.

Roman Disasters by Jerry Toner (nonfiction)

Good book by an intelligent writer.  Mr. Toner has a grasp of modern disaster theory, and it helps him make his fascinating points about how the Roman Empire dealt with them.  This book uses a highly structured style, and it helps make his arguments clear.

Worlds of Arthur: Facts & Fictions of the Dark Ages by Guy Halsall (nonfiction)

Sorry, but there was no Arthur.  The author systematically breaks apart every single tiny little argument that others have tried to use as proof, meanwhile debunking plenty of myths about the Saxon "invasion" of Britain after the breakdown of the Roman Empire.  The book is particularly illuminating about how scholars decide they know what they know.

The Saint who would be Santa Claus by Adam C. English (nonfiction)

Delightful book about St. Nicholas of Myra and gleaning the details of his "real" life from the hagiography.  His involvement in the early spread of Christianity throughout the imperial Roman bureaucracy was something I knew nothing about.