Marvel Comics is a long-time comic book publisher, one of the first publishers in the United States along with DC Comics.
In 2013, Jeff Lindsay an admirer of Marvel Comics himself, started to work with the company as a writer for a Dexter comic book series, the series ended as a limited series that run for five issues. Jeff Lindsay worked along with artist Dalibor Talajic.
In 2014, Jeff returned to work with the publisher, again as a writer and also along with Dalibor Talajic for a second volume, known as Dexter: Down Under.
It should be noted that long before Marvel had a deal with Lindsay for Dexter comics, it was mentioned in the novel Dearly Devoted Dexter, where Dexter commented on Albert Doakes: "I liked the Marvel Comics flavor of calling him Sarge."
While it's often considered a "celebrity paradox" (when a work of fiction mentions it's real creator, publisher, or, more commonly, an actor who plays a role in it), it should be noted that Dexter Novels and Comics is not the only continuity of Marvel Comics which has a fictionalized variant of Marvel itself in it. In fact it's a common occurrence.