He's worth your time. Go read him. Now.

Seriously, he's a brilliant historian and I'm always interested in what he has to write. The ones I'm most familiar with are Phantoms of Remembrance, Living with the Dead and Furta Sacra - the latter is a foundational text and classic for the study of relics and central medieval piety. He's also got some super influential articles published too (some of which are included/incorporated into Living with the Dead) and, while I havn't read his latest work in any huge detail, he appears to be doing lots of interesting stuff involving sensitive use of genetics to explore the "Age of Migrations". Obviously, no historian is ever right about everything, but Pat Geary's work is definitely a worthwhile way to spend your reading time.