You asked for it...
Some of my favorite books of all time are the Queen's Thief series by Megan Whalen Turner: "The Thief", "The Queen of Attolia", "The King of Attolia", and "A Conspiracy of Kings". Each one gets better and better. Don't read them out of order. They're set in an old Greece-like world with an original pantheon of gods - not sure that's fantasy, exactly, but it's pure gold. There's at least one more in the series coming (I hope!), and I hope it has a map! You definitely should try Diana Wynn Jones. "The Dark Lord of Derkholm" is one of my favorites. Its sequel "Year of the Griffin" is great, too. "Howl's Moving Castle", with its sequels "Castle in the Air", and "House of Many Ways", and "Unexpected Magic" (an anthology; the last 1/3 is the novella "Everard's Ride", which you should read first, in case you don't like the short stories) are some of my favorites of hers. "Hawksong" by Amelia Atwater-Rhodes is the only book to have the dubious privilege of being reread twice in a row. I finished it at 2am and immediately flipped back to the beginning and read it again, all the way through. That's not saying it's the best book here, though. Unfortunately, its sequels (in my opinion) get worse and worse until (SPOILER WARNING) the heir to the throne abdicates in favor of her uncle's illegitimate daughter (and, she believes, peace), running off with her lesbian lover. I pretend Hawksong stands on its own. Vivian Vande Velde's "Heir Apparent" and "Dragon's Bait" are a couple more favorites. Robin McKinley writes both some fantastic fairy-tale retellings ("Beauty", "Spindle's End") and (fantastic) original work that are among my favorite books ever. Particularly "The Blue Sword". Its prequel is "The Hero and the Crown". "Belle: A Retelling of Beauty and the Beast" by Cameron Dokey is my favorite B&tB retelling. IF you're not counting "The Hob's Bargain" (I wouldn't) by Patricia Briggs, which only has a vaguely similar theme. She also wrote "Masques" and "Wolfsbane" (its sequel). Her Mercedes Thompson and Alpha and Omega series are also good storytelling, but I'll warn you (as I wish someone had warned me) that there's explicit sex in them, in case it's something you'd wish to avoid. "The Goblin Wood" by Hilari Bell. Gerald Morris writes a hysterical series retelling Arthurian legends. He's finally finished it; I think there are ten.The first is "The Squire's Tale", the second is "The Squire, His Knight, and His Lady", and the third is "The Savage Damsel and the Dwarf". So that gives a hint about the mood :) Some of them are best enjoyed in order; some kind of run concurrently, or one inside another; just read them in order to be safe. If you're familiar with the story of King Arthur, you'll be prepared for the final two books, which are downright depressing. The rest were great - you don't need to read those last 2 if you don't want to :) T.H. White's "The Sword in the Stone" (part of "The Once and Future King", which I haven't read yet) is a fun tale of King Arthur before he becomes King. The Disney movie is almost exactly like the book. Kathy Tyers has a Christian science-fiction trilogy I really like, "Firebird", "Fusion Fire", and "Crown of Fire". Patricia C. Wrede has The Enchanted Forest Chronicles (4 books), but I didn't like the two in the middle ("Searching for Dragons" and "Calling on Dragons") as much as the "bookends" ("Dealing with Dragons" and "Talking to Dragons"). I might like her "Sorcery and Cecilia" series better (written with Caroline Stevermer). I also lover her "Snow White and Rose Red". Shannon Hale's "Goose Girl" was good, although I didn't like the sequels as much as the original. So those are some of (most of) my favorite books. Some of them are significantly below my (and probably your) reading level (I'm 22), but I still read them over and over. I don't think any of them are any "younger" than the other books you listed. Many of these authors have other books that I either just haven't read or didn't like as well or at all, so explore and you'll probably have more than enough material for the summer :) I hope you enjoy these as much as I have. P.S. My favorite book is "The Count of Monte Cristo" (PLEASE don't associate it with the movie, which is practically a completely different storyline with similar character names!!) My edition, by Modern Library, which I bought at Barnes & Noble, has 1462 pages. If you can read the Lord of the Rings and the Hobbit, you could literally read this, although it doesn't mean you'd necessarily enjoy it. It has a lot of history in it. But the plot and many sub-plots are beautiful. My edition, like every English edition, is a translation from French, and I am recommending not just the story itself, but my translation - I can't guarantee that another translation will be as enjoyable. Sorry. Thought I'd put in my oar, since you're looking for good books :D