I absolutely love The Heir Chronicles by Cinda Williams Chima. There's three in the series, the first one being The Warrior Heir. This isn't technically an adult fantasy, but I'd say it's probably more mature than the other two I'm recommending... it would probably be best suited for middle school and up.
I also really like the Percy Jackson and the Olympians series by Rick Riordan - it's Greek mythology told in the modern time, kind of like BBC Sherlock, if you watch that show. It's also quite humorous at times-- I love his writing style.
Inkheart by Cornelia Funke is another good fantasy novel - it's very rich in imagery, so you feel like you're really in another world.
Hope this helps! I might be back with more later.
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edit: I just saw that you're already reading Percy Jackson... keep it up; they're all great. Rick Riordan also has another series about Egyptian mythology. I never really got into it because of time, but I suspect it's just as god.