There will be 3 profiles, one that has a small base for the first and last book to rest on. If you are worried about adhesion issues with the thin base, then make sure you use the profile with a brim. Other than the main profile, the infill is kept low to save on filament and print time, so if you want more heft, you will want to add more infill.
The second profile is more decorative and does not have a book base, and do better with hardback books that can stand on their own. I added the base in Bambu studio so you can modify it easier if you want to make some adjustments within the slicer.
We have a lot of great stuff over at the Patreon: https://www.patreon.com/WilliamsIndustries
Patreon includes commercial use on all prints.