In the late 1970's I was doing a radio program of medieval music (alas, you don't hear this kind of thing on the radio these days) and I was into all things medieval. I wore out my first copy (paperback) of this definitive and engrossing two-volume set and snatched up a hardcover copy at a library book sale. I still find it handy for a quick and reliable (though somewhat dated here and there) reference. ( )