In my fifth and sixth grade classroom, there was a decent-sized bookshelf in the back, with the couch and reading area. This thing was packed. There must have been 800 books in it. When you put one back, you had to search for a shelf with some slack, so you didn't have to cram it in.
Our supplemental reading requirement, one aside from the novels we read in class, was to read 12 books from this shelf, and do book reports to prove it. Now, most of these books were pretty standard "free book" fare. Babysitter's Club, Choose Your Own Adventure, and Goosebumps were among the more cultured of the main section. However, the back section was all Newbery medal winners and nominees. Of the 12 books, 6 had to be from this section.
I was a somewhat avid reader, and decided to get the "required" books done first. The first was A Wrinkle in Time. The second was Maniac Magee. Needless to say, these books were pretty different from what I had been reading up until then. It was like listening to The BSB for years, never knowing that there was other stuff out there. I ended up having trouble finishing reading the other six, "normal" books. I've since reread many of these, and read more from the list.
The Newbery Medal is truly a mark of excellence for novels, in general. Granted, the protagonists of the stories tend to be rather young, but if you remember being young, they are good for everyone.