It was ok, though mainly a teacher's resource and guide to the Middle Ages and a small (exceedingly small) sample of young adult historical novels set in that era.
Barnhouse tries to be unbiased, but she too is a creature of her education and it would be an excellent idea to read through a number of the source books found in the back to fill in gaps, esp. about the Catholic Church, religious practices, preservation of classical learning, calligraphy, illumination, a more thorough understanding of feudalism, monarchy, and guilds, as well as general practices, manners and details of life throughout the various periods of the Middles Ages.
Barnhouse admirably tries to correct some common errors about the Middles Ages as either a period of no learning (which is patently false) or as a time when reading and writing, not to mention books, were common. Both are false and the truth lies somewhere in between.
My favorite quote was:
The writers who research carefully enough to understand the differences between medieval and modern attitudes, between different medieval settings, and between fantasy and history, can help their readers understand a strange and distant culture: the Middle Ages. Writers who create memorable, sympathetic characters who retain authentically medieval values teach their audience more than those who condescend to readers by sanitizing the past. trusting readers to comprehend cultural differences, presenting the Middle Ages accurately, and telling a good story results in compelling historical fiction, fiction that, like medieval literature in its ideal form, teaches as it delights.
My personal problem that I most frequently find in historical fiction was something that was not addressed much and that is the dialogue sounding either too modern or entirely wrong for that particular time period. Drives me crazy when historical novels mess that up.