
I have written over forty historical novels for middle grade readers. Research is an old friend, a good friend, and I employ all its tricks and tools to enrich my fantasy novels. Two great sources:
http://www.bookfinder.com/
which links thousands of small rare and used bookstores
(and a few large ones)
and
http://www.uidaho.edu/special-collections/Other.Repositories.html
The University of Idaho maintains a massive, worldwide list of primary source repositories. I have used it extensively; it's remarkable.
Primary sources are diaries, old newspapers, rent receipts from the 1800's, illuminated manuscripts for the 1200s, any kind of record left behind by real people. Fascinating!

