I don't know if I've said, but I work in the library (circulation coordinator) at a private school for grades 9-12. Part of my job is to make recommendations about YA (Young Adult) and general fiction, but it's harder than it seems. We're an academic library, but we have a largely residential (boarding school) population of 1,000 highly literate students aged 14-18, as well as younger children in faculty families and adult faculty and staff. How much of our resources should be addressing reading needs for the whole community, rather than just the classroom student? The developmental difference between 14 and 18 can be enormous at times, minimal at others. The publishers give age recommendations their best guess, but it's hard to tell...do the Harry Potter books really only appeal to grades 6-9 (ages 11-14)? :-)
I used to excuse my YA reading by saying I was reading books with my sons, now I can say it's for my job! The truth is I truly enjoy YA books for my own sake. The books are generally quick reading (great when you're very busy and/or get sidetracked easily); they address relevant topics, often from creative viewpoints; and, they tend to be much less long-winded and more to the point than traditional adult literature.
Some that we've enjoyed are...
Among the Hidden (first of The Shadow Children series) by Margaret Peterson Haddix, a futuristic society seen through the eyes of illegal "third children" in a society where the Population Police enforce the "two children per family" law
Castaways of the Flying Dutchman (and sequels) by Brian Jacques (of Redwall fame), about a boy and his dog who are given immortality and wander through the centuries helping those in need
The Last Treasure by Janet Anderson, about two cousins who meet for the first time, working through strained family relationships, coming of age, and some terrific puzzle solving
The Drift House: the First Voyage, by Dale Peck, sort of like Narnia, except it's post-9/11 and instead of a wardrobe leading into the woods the whole house sets sail on the Sea of Time, with pirates, mermaids, a sentient dumbwaiter and lots of excitement. There's also a fairly recent sequel that I haven't read yet.
Favorites from my own YA days include Gene Stratton Porter's Girl of the Limberlost series and the Mushroom Planet books by Eleanor Cameron. I don't know if they qualify as YA, but at the same time I was loving I Capture the Castle by Dodie Smith, I was also loving Christopher Morley's Parnassus on Wheels and The Haunted Bookshop about a traveling book seller in early 20th century New England.
For creepy, try Shirley Jackson's The Haunting of Hill House, though perhaps terrifying would be a better word! And Jean Plaidy (aka Victoria Holt) for historical romance.