What books do you like that are either set in medieval times or actually from that time period?

I'm reading Crispin:The Cross of Lead right now.

Once and Future King by T.H.White is great fiction/fantasy. (Synopsis here.)

Some interesting quotes here.

Boiardo's "Orlando Innamorato" and Ariosto's sequel "Orlando Furioso" are hilarious romps about knights fighting for Charlemagne. Both were written about 500 years ago. For Furioso, I'd recommend the Barbara Reynolds translation.

Best of luck,
--S.F.