The manuscript of Thrones is available to read in a research centre at Wheaton College, Illinois (just outside Chicago), and where I spent a day or so and some frantic lunchtimes tearing through it and other DLS stuff. There's quite a bit of interesting stuff that Jill Paton Walsh did not use in her continuation. (I know that many people would rather have the novelization, but I'm the History of Middle Earth reading type myself, and I'd rather have the bits and pieces of original.)