I have answered this question so many times, I decided to dedicate a web site to answer this question. Here it is:
http://www.life-after-harry-potter.com
Included is a list of only the best sorcery fantasy books, grade reading level, a short review of each book along with a brief summary of adult content. There is also a "Readers' Choice" list of favorite books, and a list of heroine sorcery fantasy books, plus a full review of "The Golden Compass".
"A Spell for Chameleon" is the most "teen" (teen fantasy adventure with a romance angle kind of thingy), but all of the books at the above link are excellent fantasy. Read the descriptions to see if they are what you like.
All of the following are excellent scifi (author, followed by books). * in front of books that involve teens as main characters, ** in front of those that involve teen romance (if that's what you mean by "teen")
Jules Verne - free online
*Journey to the Center of the Earth (my favorite scifi)
20,000 Leagues Under the Sea
Mysterious Island
H G Wells - free online, and roughly half-length novels
War of the Worlds
The Time Machine (downer ending)
The Invisible Man (unlike many IM stories, he's a villain. This is the original)
Isaac Asimov
I, Robot (you *must* read this - the only "must read" scifi)
Elijah Baley books - http://en.wikipedia.org/wiki/Elijah_Baley excellent both as scifi *and* as murder mysteries - the best of both worlds (warning: adult content in the 3rd book)
*Foundation Series - *the* classic scifi trilogy (teen in the second book - really excellent! Fair amount of romance in the third book)
Andre Norton - *the* classic female scifi author, most of her books involve "coming of age" and pure scifi adventure
http://en.wikipedia.org/wiki/Bibliography_of_Andre_Norton
her best: *Star Man's Son (also titled 2250 A.D.)
other excellent:
*Judgment on Janus (a little romance)
*Forerunner series
*Central Control series
*Solar Queen series
The Time Traders (Atlantis, magic - very cool!)
*The Zero Stone
**You may also like Andre Norton's "Moon Called", a woman with psychic and magical powers comes of age in a post-nuclear holocaust world with - well, wait until you meet the *real* villains!
*Another excellent: Mrs. Frisby and the Rats of NIMH. Though written for younger readers, I read this recently and it is great! Better than the movie (which was also pretty good). (Only tragic romance - the main character's beloved husband is dead, but she thinks of him often)
I hope this helps.
Jim, http://www.jimpettis.com/wheel/