I am with Toddos
Face out /Face up, book shelves is:
1) a SELLING tool (I also ran a bookstore sometime in my life
)
2) only used in
Real Libraries(tm)
for the 'featured/New Titles area
You wouldn't do this with very many deqd tree book (Ikea does sell
lots of 'Billy' in my area)
I do
occasionally use the cover browser and find t approximates a loosely filled shelf (where you peek into the gap as you move books)