The Rithmatist by Brandon Sanderson has an awesome math-based magical system (geometry in particular), and I can’t wait for the next one.
The Giant Slayers by Iain Lawrence is an excellent piece of story-telling, and really brought the time when polio was a problem alive to me.
Black Dog by Rachel Neumeier might be the only vampire/werewolf book I’ve read, and it was great. It’s not your typical teen paranormal romance at all.
Magic worked through honey makes Chalice by Robin McKinley one of the most unusual and interesting books I’ve read.
I wasn’t sure about including Magpie Lord by KJ Charles, until I realized that I just read it for the third time since I bought it… in June. (I re-read books a lot, but usually not that frequently.)
The Tropic of Serpents by Marie Brennan features an asexual character!
Fire Logic by Laure J. Marks is full of non-standard sexualities, relationships, and family structures–that is, in the world of the book they are completely normal, but in this world they would not be. The magic system is also fascinating.
Eleanor’s Story: An American Girl in Hitler’s Germany by Eleanor Ramrath Garner was an intense read, and also brought a particular period in history to life for me.
Jack by LC Cate featured cross-dressing/genderqueer characters in the Wild West, and it was great.
Spindle’s End by Robin McKinley is a lovely, dreamy fairy tale re-telling, set in a fascinating world.
Notice that four of these books were also on my “Top Ten Books I’ve Read So Far This Year” list in June. Since I pulled together this list in order, starting at the beginning of the year and working forwards, they’re at the top.