He's... strange. For Joker, I mean.

There are typically three archetypes Joker embodies: the Clown (Caesar Romero, Keith Richardson), the Kingpin (Jack Nicholson, Mark Hamill), and the Crazy (Heath Ledger, John DiMaggio).

Leto is definitely the Kingpin archetype. He revels in dominance, is goal oriented, and ruthless in the pursuit of his goals. He doesn't do it to have fun, but he does have fun doing it. He has a philosophy of the Joke, but he doesn't preach it like the Crazy does.

His mannerisms are new for a Joker, but often rather interesting. One particular new quirk is a tattoo on the back of his right hand that portrays a laughing mouth, which he places over his and other people's mouths, so that the tattoo makes it look (somewhat) like they're splitting a gut. It's creepy and disconcerting and I think that's the joke.

Possibly the most unusual part of Leto's Joker, though, is the fact he displays a more genuine fondness for Harley than other versions do, to the point of putting himself in danger to protect or save her. Now, you can easily argue that he still sees her as a possession and not a person, and that his actions are about protecting his property rather than actual affection, but he doesn't show much concern for property in other cases. Personally, I think this Joker sees Harley as a work of art, a masterpiece he has chipped and molded to psychotic perfection, and he's protecting that masterpiece rather than a person or property.

He's definitely a new Joker, much like Ledger was. We've not seen anything like him. I don't think he's as engaging, however. Ledger was a philosopher who saw through the self-delusion humanity wraps itself in for comfort, and strives to tear it away. Leto is a gangster with an unusual style and philosophy. End result is that he's not as intriguing nor as much fun, and it's capped off with the fact that Suicide Squad doesn't make good use of him. I do think he has potential, however.