Why would OP need to tell us? From what I can tell OP has only played with this villain for less than 1 orbit. His normal/smallish bet on the turn followed by a bomb on the river indicates that he had some sort of equity on the turn whether it be a made hand or a draw. If a true maniac bets pot on 3 streets their range could be as wide as any 2 cards.

I would actually tend to play hands passively against him. Since he's the maniac, let him do the betting for you.

You couldn't have paid me to get up from this game. Why did you leave after an hour? I would have tried to play as many pots as I could against a player like that.

In general passive lines work better against maniacs but we shouldn't just typecast all players as the same. For instance I know some maniacs that will at times play reasonably passive and other times will shove 500bbs in the middle preflop with air just for the heck of it. Some maniacs would 4bet pre with Q6 rather than call. This particular player has already shown us that he will call (play passively) with weak holdings both pre and post flop. Raising with AT preflop is good not only for value but to isolate him from other players still left to act.

Call pre assuming no short stacks/anyone to your right looks like they are about to bomb it.

I probably call all the way unless I have some sick soul owning value read on him where I know I have the winner and he'll call my river shove.... And like I rarely/never do so I just call.

Maybe. Some players including LAGs be small ott with all of their range. I think everyone agrees then that you call down all reasonable bets. I just added: don't cold A10o if you aren't willing to call down.

I also like this line against this player. 3! preflop for value if you think it's necessary for isolation. Otherwise just call and play the inflated pot with position and a hand that's stronger than his range.

NLAP makes a good point about the river bet-sizing. I'm still calling the river, since it's only been an orbit and I don't have enough bet-sizing information on him to know if this line is how he plays value or how he plays everything.

The nice thing about calling down maniacs for value is that it will eventually take them off their game. This guy is in it for the testosterone rush of betting people off their hands and proving he's a risk-taker. Losing $300-350 a couple times to someone who "just" calls you is a real buzzkill. He'll eventually switch tactics when heads-up against you, and that's when you get to start really exploiting him.

Every street played perfect IMO