The execution, the details, were interesting. I do think that Sean Murphy bent a little things: if Jack Napier were a truly good man, as he's presented here, and had to account for everything that the Joker did, then I think he'd be slightly more shellshocked. Now, I could buy the argument that he was so overwhelmed that he ended up placing all his hopes of forgiveness in Harley Quinn - but that's not how this is presented. It's presented as he feels bad, whoops, let's save Gotham now. (Although a lot of his redemption is all about Harleen, so that was kinda weird, too.) He was a little... off with Harleen, too? Maybe it was calling her Harley, which seemed weird since they were trying so hard to disassociate themselves from their former lives. But there was something else, where it was all too cut and dry: her accepting him, his complete devotion to her, and I found it too far off form The Joker to really be buyable.
Then again, some of this could be explained by the final reveal, although I don't want to go into details: this is well worth reading, and it's worth reading not knowing what's coming in my opinion, so I won't spoil that.
There's so much elegance in this story that it didn't seem more than a star off, and I think the story focuses enough on other things that I couldn't really say this flaw overtook everything. I also think when the love story between The Joker and Harleen doesn't take over? This story is a lot stronger.
And I'm not spoiling things when I say The Joker goes sane or Batman is in Arkham. The tagline on the back is The Joker goes sane, and the first page or so has Batman in Arkham. It's all about the small reveals leading up to the big one at the end. It's a slow burn that's dealt with perfectly for the most part.
Lovely story. I'm definitely going to look into reading more by this writer/artist.