These books are stored inside the shelfs at Agastya Base, a prison located in outer space directly above the Southern Base.

Kamen Rider

Kamen Rider V3

Kamen Rider X

Kamen Rider Amazon

Kamen Rider Stronger

Kamen Rider (Skyrider)

Kamen Rider Super-1

Kamen Rider ZX

Kamen Rider Black

Kamen Rider Black RX

Shin Kamen Rider

Kamen Rider ZO

Kamen Rider J

Kamen Rider Kuuga

Kamen Rider Agito

Kamen Rider Ryuki

Kamen Rider 555

Kamen Rider Blade

Kamen Rider Hibiki

Kamen Rider Kabuto

Source: https://twitter.com/Martian_Ranger/status/1483152142185603073?t=4K-A8aFpY-PYvlhOmIcK6g&s=19