So far as I can ascertain, this "comic book" purports to be the "unauthorized story of Gotham's dark knight detective." 
Detective Comics #622 is an issue of the series Detective Comics (Volume 1) with a cover date of October, 1990.
Synopsis for "Dark Genesis!"
Alfred gave Bruce a comic book about the "unauthorized story of Gotham's Dark Knight Detective."
In the comic, Lucifer attempted to renounce his rebellion and in order for him to set rights to the evil he had spawned, he found an avatar in Simon Petrarch, who agreed before they began fighting corruption and evil together. A few months after joining forces, Simon Petrarch became Batman in Gotham City.
Bruce tasked Alfred with looking into Tod Nathan Taylor, who was publishing the comic, while a killer wrote Batman's name with Billy Canfield's blood. Afterwards, the killer, who claimed to be Batman, called Jack Hemp during his show on WGTH and confessed to doing it. The killer urged Hemp to read the Batman comic to understand why he killed Billy Canfield.
As the real Batman attempted to save a woman from being robbed on the street, both of them were terrified. Then, he spotted a copy of the comic and the ground and read it. After reading it, Batman made plans to confront Fred Lasker, who was the writer.
Appearing in "Dark Genesis!"
Featured Characters:
Supporting Characters:
Antagonists:
- Batman (Clyde Harris) (First appearance)
Other Characters:
- Billy Canfield (Single appearance) (Appears only as a corpse)
- Ernie
- Fred Lasker
- Henry (Voice)
- Jack Hemp
- Tod Nathan Taylor
- Unauthorized Comic Book Characters:
- Batman (Simon Petrarch) (First appearance)
- God (First appearance) (Voice)
- Lucifer (First appearance)
- Sing-Cha
Locations:
- Real World
- Unauthorized Comic Book
Items:
- An Unauthorized Batman Comic Book
Vehicles:
Notes
- The first half of this comic prints an "unauthorized" Batman story. The imaginary story is written by a comic book writer who lives in Gotham City. In essence, the first half is a comic book inside a comic book.
- Flint Henry illustrates the "unauthorized" Batman comic book. Mike McKone and José Marzan, Jr. illustrate the rest of the story.
- This story is reprinted in Batman: The Dark Knight Detective Vol. 6.
See Also