Susan, I might have mentioned it here before, but Becky Chambers' The Long Way to a Small Angry Planet scratches a lot of the Firefly itches: a small crew in a big complicated universe, just trying to get along. Plus some cool aliens, and sex.
I also think The Martian (the book) might work for Buffy fans, because it's fast-moving and has a lot of humor. (You can skim the mathy bits.)
Maybe the Expanse novels: also a small crew of a ship with space adventues. (James S.A. Corey.)
Mogget- it was fantasy not science fiction but the 3-Body Problem looks interesting and will now go on my tbr list. (i.e, Thank you!)
Buffy fans might like Julie Kenner's Carpe Demon series. Or the Harry Dresden books, but I assume those are already on the list.
Buffy/SPN/Sleepy Hollow -- Kat Richardson's Greywalker series, Kim Harrison's The Hollows series
I think Buffy people would also like Amy's Cold Kiss.
I was just thinking about Firefly last night and how I generally don't like space or westerns, but I like Firefly, and when I try to think of something like it I come up with nothing. I think people in general would think of recommending other space-type things.
Maybe the Expanse novels: also a small crew of a ship with space adventues. (James S.A. Corey.)
The Rocinante crew doesn't map exactly onto the Serenity crew, but they're strongly reminiscent.
I think of the Vorkosigan novels as their own fandom, so I can't easily map them onto another one. Doctor Who, maybe?
I think Buffy people would also like Amy's Cold Kiss.
Oooh, I concur.
As I note in my Hilbrow piece today, Game of Thrones fans would like Fritz Leiber.
In fact, if you've ever thought, "Damn, they totally should've hooked up Brieth and Arya to tromp around and get into trouble and snark at each other" then that's basically a gender-swapped version of Fafhrd and the Grey Mouser.
How about the Vorkosigan novels for Babylon 5 fandom?