I would certainly grab as many versions of spiritual books as I could. For example, the Bible, Koran, Vedas, Pali Canon, etc.
If we get medievalized, theology would probably be very useful (simple set of dos/do-nots for civil society, common belief system to help people collaborate instead of compete, etc.)
The Abrahamic ones would be particularly useful since they have a lot in common. Of course, that could also be undermined by the narcissism of small differences...