Book-On

Book-On is a bookshop that can be found in Academy City that is based on the Japanese bookshop, Book-Off. The establishment is fairly spacious and contains a variety of books for sale, as well as CDs and DVDs; the store lies across the road in front a dark alleyway, this is where Touma discovers the remains of Misaka 10031 during the Sisters Arc.

The bookshop only appears in the anime in both adaptations.

Background
The novel uses an unnamed bookstore as selling used books. Since the anime based the name of the bookstore of an existing used bookstore seller, it is logical to infer that the anime's bookstore sells used books alone.

Toaru Majutsu no Index
The store is featured during the Sisters Arc, where Touma who is accompanied by Misaka 10032 and her cat tries to buy a reference book on how to take care of cats for Index, as she did poorly in removing fleas from Sphynx – her cat. Touma leaves the cat to Misaka 10032 who waited for him until she sensed Accelerator and another experiment was to take place, she leaves her cat at the entrance of the store before taking-off to do her duties.

After buying the reference book, Touma finds that Misaka 10032 was not outside and has left her cat at the entrance of the store. Touma later leaves the storefront to go investigate the alleyway that was across the store. Here, he discovers the remains of Misaka 10031 who was killed by Accelerator, and later discovers the existence of Misaka Mikoto clones and the experiment that they were in.

Toaru Kagaku no Railgun
The store is seen in the background during Mikoto's tenure as an acting member of Judgment. Here, she notices a man flirting with a girl – in the alleyway from across the road – and tries to break them up thinking that he was harrassing the girl, much to her embarassement as she was mistaken.