I had a similar problem with a book containing a lot of html widgets. I wasn't able to Preview it either. I tried deleting chapters looking for an error. I finally decided it was too 'big'. I split it into two books, i.e. two parts and both uploaded in the usual time, within a couple of hours.
How complex is your book?
I have uploaded three books this week and last and each took a very long time to upload. One went for 18 hours.
The behavior was that the book would verify normally, start to upload, then pause for a few minutes, with an upload speed of zero K and a time to completion of infinity, then commence again for a few seconds at about 500+K upload speed and a time to completion of 30 to 40 minutes, then another pause for a few minutes with the same sequence occuring over and over until finally the very last byte of these books made it! All three finished with no errors and extreme frustration for me.
Two of the books were 400mb in size, the third was about 70mb.
I wrote to Apple about the issue and was ignored the first time I wrote, and told that the upload time depended on the capacity of my internet connection the second time (duh). By the third time I realized that any help towards a solution was hopeless. Apple support never responded to the 'furious activity/no activity' behavior at all. My internet connection is an ADSL line, that is not shared, and behaves normally for any other uploads and downloads. The behavior is more indicative of a lack of capacity on the receiving end.
I know Apple uses commercial intermediaries to receive and process the submissions. Perhaps the problem is there.
I have four more books to upload. I hope they make it there by Christmas. Of course, Apple is on vacation as of tomorrow so it really doesn't matter!
So, before you start hacking your project into pieces, since the size limit is 2 GB, I think what you are experiencing is a capacity problem on Apple's end.