"20th Century Electricity Catalog") is a Japanese light novel written by Hiro Yūki and illustrated by Kazumi Ikeda, with art and backgrounds by Momoka Nagatani.

Kyoto Animation published the novel under their KA Esuma Bunko imprint in August 2018.

20 Seiki Denki Mokuroku is a Japanese light novel written by Hiro Yūki and illustrated by Kazumi Ikeda, with art and backgrounds by Momoka Nagatani.

Kyoto Animation published the novel under their KA Esuma Bunko imprint on August 10, 2018 (ISBN 978-4-907064-88-4).

[2][3] 20 Seiki Denki Mokuroku won an honorable mention in the full-length novel category at the 8th Kyoto Animation Awards in 2017.