I've read this series since it started, and never really figured out why I like it so much. In this issue, it finally clicked; this comic is aggressively trying to be what most others desperately try not to be. It is especially the furthest thing from other Batman comics, and I love it for that.
This issue's plot is as simple as it is unimportant: Marsha, Queen of diamonds, is hypnotizing rich people into giving her their money and valuables. The plot is not elaborate, and on the ridiculous side, given that she hypnotizes them with a giant diamond that gives off the right light pattern, but the plot is far from important.
For absolutely no practical reason, the Batmobile has diamond-studded brakes. Robin gets brainwashed by Marsha and steals them to give to her, causing trouble when they are unable to stop when going after her. Then they crash the Batmobile in an area with people, and Alfred comes to pick them up, even though people seeing him there might compromise Batman's secret identity. Then there's the moment when, confronting Marsha towards the end, Batman and Robin avoid getting brainwashed by timing their blinking with the light pattern given off by the diamond.
All of these are completely ridiculous, and the comic loves that fact. It's playing this as straight as possible, the characters never winking at the camera or hinting that they get how much of a joke this is. There's just enough time spent on the moment that it feels like the writers are telling you "We know this is ridiculous, but we don't care". It finds a great middle ground, with the voice of the story acknowledging how outrageous it is, but not derailing itself to make that joke, and I love it for that.
This entire series has been those moments, and I've often wondered why I like it so much despite so often being stupid. It turns out, it's exactly because it is that stupid, and revels in that fact, that makes me love it so much. It's probably not for people who like their comics to take themselves seriously, but I love it being this way.