What are you looking for exactly?
A list of files: pg100.epub, dex.pdf, intro.txt
A list of titles: "War & Peace", "Dead Souls", "Heidi"
Full metadata: "Rebecca", "Daphne du Maurier", 1938, 9780316323703
Do you have ADB working?
It's always useful. I prefer it over any other interaction.
Code:
C:\>adb shell ls -1 /sdcard/Books
pg1.epub
pg2.epub
pg3.epub
Depending on what library app you are using you can query or extract the database of book metadata.