"Biburia Koshodou no Jiken Techou" (Casebook of Biblia Antiquarian Book Store) by Mikami En. Stories of how Shinokawa Shioriko solves a series of mysteries using hints from various old books.
Superficially similar to the Bungaku Shoujo series in how each story is centered around a single book, and how the detective role is played by a girl who really likes books. But while Bungaku Shoujo might for people who likes to read, this book is for people likes books. A lot more attention were given to the physical attributes of the individual books themselves, and there is less emphasis on the text printed in those books.
The new perspective on examining books makes this book worth reading. As a bonus, it's also a good introduction to many interesting old books. For me, having a character who really likes books is usually enough to make me want to read it.
Previous (2013-01-04): "Ningen Shikkaku"
Next (2013-01-31): "Biburia Koshodou no Jiken Techou" volume 2 by Mikami En