If you like Mossflower by Brian Jacques
Brian Jacques is hard to beat for a rousing war-like fantasy, but here
are a few titles that you might want to try. All of these books have
sequels or are part of a series.
Artemis Fowl by Eoin Colfer.
When a twelve-year-old evil genius tries to restore his family fortune
by capturing a fairy and demanding a ransom in gold, the fairies fight
back with magic, technology, and a particularly nasty troll.
Sea of Trolls by Nancy Farmer.
After Jack becomes apprenticed to a Druid bard, he and his little sister
Lucy are captured by Viking Berserkers and taken to the home of King
Ivar the Boneless and his half-troll queen, leading Jack to undertake a
vital quest to Jotunheim, home of the trolls.
Mortal Engines by Philip Reeve.
In the distant future, when cities move about and consume smaller towns,
a fifteen-year-old apprentice is pushed out of London by the man he most
admires and must seek answers in the perilous Out-Country, aided by one
girl and the memory of another.
Book of Three by Lloyd Alexander.
Taran, the assistant pig-keeper, longs to be a hero. He begins his
journey to heroism with a strange assortment of companions on a
dangerous mission to save his beloved homeland, Prydain. Taran's
adventures chronicle the brave battle he wages against the forces of
evil to protect it.
Watership Down by Richard Adams.
Chronicles the adventures of a group of rabbits searching for a safe
place to establish a new warren so that they can live in peace.