You need to try exporting the first half of the book.
If that exports ok then export the other half of the book.
Whatever half it fails on - keep dividing the book in half to find the culprit page or pages.
For example if your book is 128 pages long:
1. Export pages 1 - 63
2. If these Fail to Export then
3. try exporting1-32
4. If these Fail to Export
5. then try exporting1-16
If it doesn't fail (step 2)
Then export pages 64-128
and 64-90 etc.
until you find the pages causing the issues.
It's also possible it won't fail at all if your break it into small enough chunks. This, I think is an indication of insufficient system resources to process the file in one piece. The chunks can be recombined into a single PDF in Acrobat.
To identify culprit page is even easier with nice free tomaxxi script Control Background Export
it enables you to return to life "old style" pdf exporting progress bar and you can notice which page ID fails to export.