This also sounds a bit like Gene Wolfe's Book of the Long Sun, and your image really looks a lot like that Whorl: a cylindrical "world" where distant lands wrap around the sky, with a laser-like light source running down the middle. The "book" is actually a tetralogy; from a review of the final installment, Exodus from the Long Sun (emphasis mine):
The series is set in a generation starship, the Whorl, which has reached its destination, and is reaching the end of its ability to sustain life. The ship is a huge, hollowed out asteroid, which rotates to provide gravity. Down the axis of the ship runs the long sun, a kind of huge strip light with a rotating shade that provides night and day. At one end of the ship is Mainframe, the vast computer that controls the ship, and stores the personalities of its maker and his family.
The main character is a young man who does explore his world beyond his home neighborhood, and eventually has adventures that lead to the revelation that the Whorl is a ship and the rescue of the populace of the Whorl. He gets help from a friendly robot ("chem") as well as encountering the intelligence running the whole shebang in the city of Mainframe.
The cover of the two-book collection covering the first half of tetralogy, Litany of the Long Sun, looks a lot like your image:
An image of the original artwork, without the title text and left-right reversed, looks even more like your "inspiration" painting.
Despite these similarities there are several caveats. First, of course, it's four books, not just one. Also, Long Sun was written in the 1990s, so later than you remember reading your book. Finally, there is a huge religious element to the story, plus a gang war, which are important elements that don't match your description. I therefore don't think it's exactly the same book you remember, but perhaps you read it (or just saw a cover/blurb) and it reminded you of the other book and you connected the two somewhat?