Boosey & Hawkes, which publishes the music of John Adams, was kind enough to lend me a study score of Naive and Sentimental music a couple of years ago. They also put me on the mailing list for their newsletter.
The spring issue contained a pointer to an interactive feature on the Carnegie Hall Web site, in which the Emerson String Quartet explores the quartets of Bartók. I have not examined this in any detail, but it looks fascinating. It's oriented toward performers; I am sure that anyone who loves that music and knows something about it will learn lots: