Try exporting 50% of the pages - if it's a 24 page book - try page 1-12 - then try 13-24.
whatever side it fails on is where the error is.
Keep halving your doc until you find the culprit page(s).
From here you'll have to dig into the page - perhaps an image needs resaving. Perhaps a corrupt Text frame.
You'll need to remove half the objects and repeat the process for that page to find what's causing it.