Frank Miller's 1986 Batman: The Dark Knight Returns defined the Batman forever. In 2002 Miller wrote and drew the sequel, Dark Knight Strikes Again, which got a lot of mixed press. The 1986 book certainly had elements of parodic art, but the overall tone was serious and operatic; the sequel dangerously veers between, and combines, the sublime and the ridiculous. I think the result is fairly brilliant and fun, but I understand why people didn't get it. The art is garish and (intentionally) loose and sloppy; the coloring is insane (but again I think audacious and fantastic), often falling outside the lines in huge swathes of large, pixilated blocks. I want to grab just three moments (and, for now, avoid talking about his recent All Star Batman run, in which he has, at least for the moment, lost me).
Superman and Wonder Woman have sex in the air over seven pages and then fall to earth together, smashing into the ocean and knocking over an aircraft carrier in the process. Miller is a big fan of pulp novels, and though the scope of the pulps is very different, he keeps that overwrought sensibility: where a pulp novelist would have written "and the aircraft carrier was knocked over, the planes falling into the ocean like toys," Miller draws them like little toy planes.
The image is childish because it is the visual equivalent of a cheesy (but lovable) metaphor.
Similarly Lex Luthor is a monster, and so Miller draws him as a hulking ape. He doesn't go for "cool" dark shadows (as Spawn would) because he doesn't want us to be in awe of Luthor, he wants us to fucking hate him.
In the scene at the end of the first issue, Batman beats the crap out of Superman with a pair of Kryptonite gloves; the issue ends with the words "Get out of my cave." The image is grotesque and the colors match as the movement of the gloves is captured by pixilated green swathes, a bold choice by Lynn Varley -- one of the best colorists in the industry along side Laura Martin (nee DePuy) and Jamie Grant. There is an American literary tradition of showing the grotesque, including William Faulkner, and Flannery O'Conner, and we should judge Miller's Batman in this context, and see his portrayal as a good thing. The word "grotesque" comes from "grotto," a cave, because we imagine that cave dwellers, like Tolkiens's Golem, become deformed and weird; it was only a matter of time before Batman, in the Batcave, was shown in the same way.