As I did not have time to sit and wait for Apple to fix this, I connected my ipad to the computer and went into iTunes and selected "Books" from under my device. This shows a list of the books that are on your ipad.
I then systematically started deleting documents a few at a time, and trying to open iBooks on the ipad after every set of deletions. Eventually, after I deleted about 30 documents, iBooks loaded and is not crashing.
I started with books that I had purchased through itunes, none of those seemed to be the cause.
From there, the rest were all regular PDFs.. So, from what I've seen, the cause is likely something about particular PDFs that is causing iBooks to crash.
For anyone that needs to get iBooks working immediately, I would suggest backing up your device to computer, and then go through the list of books on your device as I did and start deleting a few at a time, trying iBooks to see if it crashes between every set of deletions.. Note that unless you have copies of the documents elsewhere, deleting the books this way does DELETE them and you will need to move them back onto the ipad from your original sources.
Good luck!