Is there an official adaptation of this series?

A faithful 74-episode anime adaptation produced by studio Madhouse exists, which covers the entire story of the manga with high precision.

Are there any supplementary books related to the story?

A tie-in novel titled Another Monster exists, which is presented as an investigative report and provides additional details and context not found in the original manga or anime.

Naoki Urasawa's Monster, Volume 8: My Nameless Hero

My Nameless Hero

Manga Crime Psychological Thriller

Pages: 216
Published: 1998
Language: English

Synopsis

Tenma is hot on Johan's trail and he's more determined than ever. Now in top physical condition and armed with a high-performance sniper rifle, has Tenma acquired the keen hunter's edge necessary to bag his prey? Or will his physician's instincts prevent him from carrying out his dreaded task?