For me, books and trips just go together. They are a mutual aid combo: the books enhance the trips, the trips enhance the books. The books fall into several classes:
1. Books acquired specifically for the trip
Books to read in transit
Rest time reading
2. Books acquired during the trip
Local color fiction or non-fiction
3. Books acquired after the trip
To fill in the blanks
4. Sometimes there's the book that made me want to take this trip in the first place.
5. And the books read long before the trip that come back to mind during the trip.
What is selected depends on the purpose of the trip: tourism, relocation, family stuff.