Through the years I have read hundreds of books, and i have noticed that I see less and less stories that end without a happy resolution. i recently went back and read 1984 and I am Legend, While these were amazing books, neither one of them would have what I would call a happy ending. I can't be the only one who liked this style of writing, i just can't seem to find any current stories like this.
You might like Chuck Palahniuk books then. Twisted stuff and very few happy endings.
A couple of Heinlein novels come to mind: Podkayne of Mars and Glory Road. The release I own of Podkayne has the original ending an an alternate, which can hardly be called, "happy." Glory Road may be a touch more upbeat, though considering what Oscar Gordon is forced to confront after he supposedly wins the day, I wouldn't call it fully a happy ending. Heinlein's Moon is a Harsh Mistress has more of a "life goes on" ending to it, though it has serious losses among its leading cast.
And thinking of downright downer endings, Huxley's Brave New World is right up there, now that I think about it.
I HATED the ending of The Cat Who Walks Through Walls, even though the title tells the reader that somehow Pixel continues to live....apparently forever. (In To Sail Beyond the Sunset.)
Ginny Heinlein left the real Pixel with David Gerrold when she moved to Florida after RAH died. The cat vanished/ran away...something. Mr. Gerrold was living in this Valley then....we are surrounded by coyotes and other predators that have been displaced by housing developments. Dog walkers need baseball bats or golf clubs...cats live indoors 24/7.
I have some Polaroids they sent me of both Heinleins AND Pixel in the Bonny Doon house. And I CAN'T FIND THEM! (I have to dig through a roomful of papers and stuff soon.)
I prefer a "happy ending" but not at the cost of character development or plot. You see a lot of movies in paticular with a happy ending tacked on, and its just so annoying.
Mercedes Lackey explained her idea of why Fantasy fiction and detective stories are so popular...everything works out in the end. Sort of.
One of the most unhappy endings I've ever read, was a short story, "The Cold Equations," by Tom Godwin. It's in several SF anthologies. (And has been roundly criticized as "bad engineering." I agree.)