Yes, it is. If you ask me, it's essentially at the same level as "The Man Who Laughs": likable, but not mind blowing.
Ok, so, Batman tries to stop the Joker who's trying to prove a point; that anyone who's push far enough will want to escape reality through insanity. As such, Joker's own origin (which I still don't care for) is shown as a testament to that concept. Ok, but there's only one problem with that--I've never bought that the Joker is insane.
Seriously, I never have, and never will unless there's a drastic change in his character. He doesn't leave the nature of his personality up to the outcome of a coin flip, nor does he think he's from Wonderland, or anything like that. He's just EVIL, nothing else. He's still one of the best villains ever made, I might add.
All right, back on subject. This story was apparently so good that every Batman movie has gone to it for inspiration for the Joker. Tim Burton says it's the first comic he ever liked, and of course the Dak Knight used it too. It's obvious in both movies. In fact, the hilarious interrogation scene was obviously taken from here, albeit with some creative liberties employed. "WHERE IS HE!?"
Anyway, Joker tries to prove his theory by tormenting Commissioner Gordon. First he shots Barbara and it results in her becoming a paraplegic, then he kidnaps Gordon, brings him to an abandoned amusement park, has his lackeys electrocute him with cattle prods, and makes him see nude pictures of his daughter suffering. Joker eats it up, even though he fails at driving Gordon insane. Then Batman shows up and stops him. Yep. Then before he's arrested, Joker tells a joke that Batman actually laughs at. This part seems really messed up. After the sick crap Joker just did, Batman's LAUGHING with him! It's wrong on so many levels.
The art is very good, even though it isn't anything that interests me. I got the deluxe reprint where they recolored it. I found a few images from the original print, and I say it's definitely an improvement. However, apparently it's a tradition that whenever you get joker venom in your system, you're skin and hair turn to jokers colors. I've said It once, and I'll say it again, I hate when they do this. But to be completely honest, I like the art in "The Man Who Laughs" better, even though they do the color change crap more frequently.
So overall, I like it, but it's overrated, like something else Batman related...
I must say, though, Joker's song was one of the awesomest things I've ever seen.