The most uplifting books I’ve read in recent years are the No. 1 Ladies’ Detective Agency novels, by Alexander McCall Smith. There’s a bit of a romantic subplot, but it’s very sub-plotty.
Oh and, the opposite of uplifting? King, Straub, etc. Maybe what you need is a break from such stuff? I know reading too much of that kind of thing can affect my outlook, personally.
I always recommend James Herriot’s All Creatures Great and Small series as uplifting books. Not only are they funny, but they’re about a man who realizes over and over again that he’s living exactly the kind of life he wants to be living.
The Curious Incident of the Dog in the Night-time by Mark Haddon. It isn’t a long read and is written for young adults, but it is simply brilliant. Don’t skip over the math - it is simple and inspiring in itself, and you will lose the brilliance if you do. And please don’t let the mention of math put you off. I have had many non-mathematical people absolutely adore this book.
I don’t usually associate ‘uplifting’ with sci-fi or horror. But Asimov’s Foundation novels always get my mind off of whatever’s bothering me. You can find the full list here. Look for the heading ‘List of books within the Foundation Universe.’
When I need someting uplifting, I usually turn to movies and comic books. Gattaca is uplifting sci-fi and Fright Night is uplifting horror (kind of). For uplifting comic books, I’ve enjoyed Daredevil: Born Again and Batman: The Cult.
I may be in a minority, but I find John Irving’s A Prayer for Owen Meany to be very uplifting. It has some very sad moments (as well as several funny moments), but the overall message is that everything, even bad things, happen for a reason.