"Batman #23.1: Joker" by Andy Kubert and Andy Clarke brings nothing new to the table when it comes to the story of one of the best villains ever to grace Batman's universe. Additionally, short of some strong visuals by Clarke, the book is essentially a blemish on an otherwise stellar (almost) two year run for "Batman."
"Forever Evil" as a concept would have made some sense next month -- it still would have been a pointless gimmick, and this book's actual quality and value would likely not have improved -- but some people will pay for unimpressive scares and horror gore in the month of October. Instead, the issue is too soon to make sense and too inadequate to function as a compelling story with or without the gimmick.
Kubert's tale lays out the abuse Joker faced as a child that made him the monster he is today and borrows every hackneyed idea from the old "abused bad guy" playbook. There's not a new concept to be seen. Well, not until you get to Joker's "present day" decision to start a family by stealing a baby gorilla from its mother at the zoo. Joker raises a "son" in the form of an abducted baby gorilla (which he calls Jackanapes, Jack for short). It's a terrible idea and one nearly impossible to execute well.
Kubert's writing is far too broad and obvious to work. He leans on cliches at every opportunity, and pushes on the boundaries of both believability and good taste too often. The story revels in being gruesome (a man is eaten alive by a giant snake, among other things), which makes a certain amount of sense given the context, but still somehow manages to come off as crass.
Clarke's visuals with solid colors by Blonde are the only aspect of merit, but even they cannot save this story. The art is also a bit inconsistent. While Clarke handles the Joker's childhood abuse in a smart way (by finding and moody and depressing balance that does a good job of maximizing the horror without being outright gory), he sometimes overplays his hand, like an added "single dramatic tear" that takes an otherwise interesting moment from nuanced to obvious. Though Kubert's back-story for the Joker is banal, Clarke's pages for those scenes are strong. It's when things get more cartoonish and action-based later on that Clarke stumbles a bit, not making the strongest choices. Clark does manage impressive expressions and visual cues for both Jack and Joker, an impressive feat that tells us far more than Kubert's writing does, but it's just not quite enough to save the book.
Short of some compelling, albeit horribly disturbing, visuals by Clarke, there's nothing of interest in "Batman" #23.1. In fact, it's odd that it even exists as a comic book. It's an idea (and execution) that should have been left on the cutting room floor.