The novels were originally published by Akita Shoten; 23 volumes of paper backs were printed. The stories do not appear in order by publication date, but in the order that Tezuka and the collection editors considered most appropriate. The collection begins with "The Birth of Astro Boy", an episode that Tezuka wrote in 1975 to make the collection of stories easier to understand. The first "Astro Boy" story ever written, first published in April 1951, is in volume 15. In addition, Tezuka often re-drew chapters that he had created earlier. Schodt explains that this is the reason some may appear "more modern" than others. For many of his older stories, Tezuka added introductory pages where he himself was portrayed as the narrator. The color pages were reprinted in black and white for the inexpensive paperback versions.