So my novel is probably going to come out just over 40k.

I'm in the same kind of situation. I just finished the rough draft of my second novel (seriously, like 5 minutes ago), and both it and my first ended up at about the 40k mark. I'm going to start revising the first, fleshing it out and adding a subplot, which I think could bring it to the 50-60k range. But for the second, I don't see it coming out more than 45k or so.

However, these aren't intended to be YA. The first is probably light enough that I could push it in that direction if I wanted, but probably not with the second. Is there a market for adult (not "adult") novels of this length?

There are literary novels around 40k, but the examples I can think of tend to be by established names - The Sea by John Banville, On Chesil Beach by Ian McEwan. I've just read Truth or Fiction by Jennifer Johnston (all of whose novels are under 70k, in many cases quite a bit under) and I estimate it to be around 38k, around the same length as On Chesil Beach.