C.J. Box's Joe Pickett series. I believe Below Zero is #9 and the author shows no signs of lagging in his diligence to take the reader on a thrilling ride through the wilds of Montana...and the heart of a family.
This series is not for the feint of heart or the squeamish. But the most difficult scenes to read are not arbitrary. Everything has it's purpose to advance the plot and, on occasion, educate the reader to the controversies of the contemporary west.
I would never put a reader off a particular book, but I would advise starting this series at the beginning with Open Season. By the time you reach Below Zero, Joe Pickett is chasing down a dying Chicago bad guy, and his seriously screwed up son, with a warped idea about how he can clean the slate before he dies. But Joe is also urgently searching for a young girl who may...or may not be the adopted daughter whose death years--and books--ago left an aching hole in the hearts of Joe's family.
Of course the elusive and mysterious Nate Romanowski has Joe's back when things turn ugly, which only makes the whole experience richer. But first Joe has to hike into Nate's remote lair where he's hiding out from the feds.
The title doesn't refer to the cold, but it certainly could refer to the hearts of these 'bad guys'. Readers can count on Joe catching up with them, but as always, we have no guarantee that there won't be collateral damage. That's the catch with Box's series: there are no promises. But I'll make a promise--if you can take it, you'll love these books!