I had the same problem. At about the same time the cover previews were replaced with a simplified form, some of the documents got completely scrambled (pg 1 from document a, pg 2 from doc b, ...), and some documents would only display the no-res version - the muddy text that pops up before a document completely loads.
I deleted all 130 pdf files and reloaded. This fixed the corrupted files. This was kind of a pain because I didn't want everything from iTunes, so it meant making 130 individual selections. It would have been simpler to remove the unwanted books from the iTunes library. I am afraid to do this because some purchased books seem to be missing from the iTunes directory.
Move seems to work if you limit yourself to a few documents at a time. Five works for me, and I've decided not to try to push further. I expect that a future version of iTunes will support moving books into collections on the computer.
