Hi, Ali! You could try Tamora Pierce's "Tortall" series. They're medieval fantasy written for a younger audience (much like Harry Potter), but I found them extremely engaging when I read them a few years ago. The last five books are larger and may take a bit longer than the first (which you will probably breeze through).
In case you decide to give them a try, here's the order you'll probably want to read them in (Taken from Yahoo! Answers)
The Tortall Series (read in this order):
Song of the Lioness Quartet
1. Alanna: The First Adventure 2. In the Hands of the Goddess 3. The Woman Who Rides Like a Man 4. Lioness Rampant
The Immortals Quartet (one of my favorites)
1. Wild Magic 2. Wolf Speaker 3. Emperor Mage 4. The Realms of the Gods
Protector of the Small Quartet
1. First Test 2. Page 3. Squire 4. Lady Knight
Daughter of the Lioness (another favorite)
1. Trickster's Choice 2. Trickster's Queen
Beka Cooper
1. Terrier 2. Bloodhound 3. Mastiff