Boneyard by Michelle Gagnon.
Some time ago, Michelle Gagnon offered free downloads of this book from her website, and I took her up on it. I was finally able to get to it (library books come first), and it was great.
In this second book in the Kelly Jones series, some hikers come across what turns out to be a mass grave in the woods. Because of the proximity to the Massachusetts-Vermont border, the FBI is called in to advise. The FBI is in the person of agent Kelly Jones, who is forced to postpone a long-awaited vacation to help on this case.
Someone appears to have been targeting young gay men who are drifters, and therefore not missed when they disappear. Or is it two someones? The investigators are led to two bodies placed together, but they've definitely been killed by two different people. Is it a copycat, or two killers working together?
Kelly is forced to deal with squabbling local police including uncooperative Massachusetts State Trooper Bill Doyle and eager-to-learn Vermont homicide detective Monica Lauer, as well as here own insecurities in order to discover the truth, which turns out to be even more disturbing than the investigators imagined.
There are some graphic descriptions of torture, which I found difficult to read, but they are few and brief, and only used to advance the story. I skimmed them, not just because of their disturbing nature, but because I really wanted to know what happened.
I'm definitely going to read Tunnels, the first in the series, and The Gatekeeper (the third).