Listmania!
Fabulously Literary YA/Teen Books
By an Amazon.com customer
Harry Potter Hardcover Boxed Set with Leather Bookmark (Books 1-5)Harry Potter Hardcover Boxed Set with Leather Bookmark (Books 1-5) by J. K. Rowling
Buy used from: $65.00
They're popular -- but they truly are well written and engaging! ;)  Also applies to #6.
Lord of the FliesLord of the Flies by William Golding
Buy new: $9.99 / Used from: $0.01
The classic exploration of what happens when a group of boys is stranded on an island.  Fascinating psychological insights and superb descriptions/images overfloweth.
Tailchaser's SongTailchaser's Song by Tad Williams
Buy new: $7.99 / Used from: $0.01
Follow young tabby cat Tailchaser as he searches for his catfriend Hushpad and his tailname.  A classic "journey/quest" story with a cat protagonist.  Wonderfully well developed.  Don't miss it!
The Catcher in the RyeThe Catcher in the Rye by J.D. Salinger
Buy new: $6.99 / Used from: $0.01
The narrator has a unique voice that catches your attention and draws you along into the story.
Fahrenheit 451Fahrenheit 451 by Ray Bradbury
Buy new: $6.99 / Used from: $0.33
Wonderful writing and a fabulous message about censorship, technology, society.
DeerskinDeerskin by Robin McKinley
Buy new: $7.99 / Used from: $0.01
A particularly intense McKinley novel -- deals with rape, among other serious issues -- based on a much-neglected fairy tale.
The Hero and the CrownThe Hero and the Crown by Robin McKinley
Buy new: $6.99 / Used from: $0.01
High fantasy featuring generally mistrusted, unpopular royal daughter Aerin of Damar and following her journey to become a hero among her people.  Precursor to The Blue Sword.
Blue SwordBlue Sword by Robin McKinley
Buy new: $6.99 / Used from: $0.01
The story of Harry Crewe, an unorthodox young woman bored with her dull life...until she is kidnapped by the king of the Hillfolk and challenged beyond her wildest imagining!
Brown Girl in the RingBrown Girl in the Ring by Nalo Hopkinson
Buy new: $11.19 / Used from: $1.17
Magical realism/fantasy in the musical rhythms of Caribbean speech.
The Garden (Teen's Top 10 (Awards))The Garden (Teen's Top 10 (Awards)) by Elsie V. Aidinoff
Buy used from: $0.71
What was it really like in the Garden of Eden?  A fresh look at this age-old story from the perspective of a witty, courageous Eve.
Riddle-MasterRiddle-Master by Patricia A. McKillip
Buy new: $12.24 / Used from: $1.68
Morgan of Hed, Raederle (the Second Most Beautiful Woman of An), and the High One's Harpist are tangled up in a fight for the world they all inhabit and love.  Outstanding characterization!
Rose DaughterRose Daughter by Robin McKinley
Buy new: $6.99 / Used from: $1.08
A poetic re-telling of Beauty and the Beast, with a significantly less shallow take on beauty itself.
The Earthsea Quartet (Puffin Books)The Earthsea Quartet (Puffin Books) by Ursula K. Le Guin
Buy used from: $12.99
Master SF/F writer Ursula K. Le Guin's series for YAs.  The books beyond #4 are included in my recommendation, too!
Rubyfruit JungleRubyfruit Jungle by Rita Mae Brown
Buy new: $7.99 / Used from: $0.01
This sharp, witty book tells the story of a poor Pennsylvania girl's coming of age as a sexually liberated young lesbian.