My 15 yr old DD has been reading Japanese horror books. Not sure if they are for adult readers or not.

Op here--thank you!!!! Great suggestions!!

the Guilded Wolves series.

This may seem weird, but I read a Mrs. Polifax book to my kids and they got into the series. The books are about a grandmother during the Cold War who is bored with her life, so she volunteers to be a spy.

Other adult books that I read as a teen:

Mystery
Agatha Christie
Phyllis Whitney
Elizabeth Peters

Historical Fiction
Thomas B. Costain - Some of these are better than others. My favorite by far is Below the Salt which has Supernatural/Time elements (unlike his other books)

Alan Drury wrote some great political fiction, which although somewhat dated sometimes seem amazingly current, in that they’re more about power and the interweaving of political structures. He was definitely right-wing (old school, not MAGA), so you have to balance that perspective when you read them

Misc.
Rebecca
Cheaper by the Dozen (hilarious biography, but sad at the end)
Flowers by Algernon - great book, I think there may be sone sex, but I don’t remember it being graphic

Great suggestions here! My teen loved some Stephen King and then moved on to autobiographies in his interest areas.

Also Sebastian Junger.

From my bookshelves my DD has read She’s Come Undone, Prep, Secret History

Not my teen's current taste but I LOVED Michener's books when I was her age. I think I started with Space, then read the Source, and then Chesapeake. Long, interesting, and entertaining!

I vaguely remember reading (and enjoying) The Right Stuff, by Tom Wolfe after reading Michener's Space. (From there I went on to read Bonfire of the Vanities, which I'm guessing may be too dated to be interesting to this generation?)

My DD loves the Taylor Jenkins Reid books (in my day these would have been banned books)