Anyone aware of any gay novels that are set in a Maine local?

No, but you might check out A Winter's Light by John Preston. It's a collection of his essays published after he died. He writes about life in Portland among other topics. He talks about why a gay pornographer and AIDS activist chooses to live in Maine after gay meccas like San Francisco and New York. He talks about watching and helping a community grow. There is also a chilling oral history he takes of a gay man living in the nightmare that is Lewiston and an essay of the murder in the '80s of the gay man in Bangor.

I don't know how old you are, but I read lots of his writing in the '90s. I remember the time, places, events and attitudes. Give it a try IF you can find it.

In Young Adult, there's Tips on Having a Gay Ex-Boyfriend. Personally, I didn't really care for it, but you might want to check it out because it seems to have a substantial following. It's told from the viewpoint of a straight girl, though, and I personally found it somewhat condescending.