Osamu Tezuka is considered the Walt Disney of Japanese animation and comics, responsible for a number of beloved characters, chief among them Astro Boy. So recasting one of the most beloved of Astro Boy's stories, "The Greatest Robot on Earth" is a tall order, much as it would be to redo a classic such as Bambi or Snow White. In this case, Urasawa plays to his strengths, recasting the story into a murder mystery. A mysterious figure is destroying the most powerful robots in the world, and one detective is on the case. That detective is Gesicht, who is himself a highly advanced, powerful robot.
As the series goes on, it redresses some of the more anachronistic parts of Tezuka's tale, with a more realistic and less stereotypical portrayal of Middle Eastern people and conflicts. The ability of Urasawa to marry ideas from Tezuka's original story with popular culture and historical references from more recent times is one of the great strengths here. The story is not a direct update but also draws on a great many pop culture works like Isaac Asimov's I, Robot and Star Trek: The Next Generation as pointed out in this substantive review by Ed Sizemore. It is this eye to include disparate elements that lends greater intrigue and depth to the story.
Naoki Urasawa is one of the most acclaimed purveyors of manga in recent times. His work on series such as Monster and 20th Century Boys has led to financial and critical success. He has won the prestigious Shogakukan Manga Award three times, the Tezuka Osamu Cultural Prize twice, and the Kodansha Manga Award once. Pulitzer Prize winning author Junot Diaz even called him "a national treasure in Japan."
Updating a classic for a modern audience is no easy task, but according to many reviewers, including Charles Tan, Urasawa's effort here is very successful. The strong characterizations in the story led Greg McElhatton to call it a "must read." One other review from Deb Aoki compares the updated Urasawa version to the original Osamu story.
For people interested in more discussion on this volume there is a substantial essay on the series on the Tezuka in English website.