The Edge Chronicles 2: The Winter Knights: Second Book of Quint by Paul Stewart
Quint Verginix has enrolled as a squire in the Knight's Academy. After his training, he will be able to pilot stormchaser sky-ships into the heart of Great Storms, and retrieve the solidified lightning - stormphrax - to weigh down the floating rock on which Sanctaphrax is built. But as a freezing winter takes hold, and the city strains to break free of its tether, ancient feuds threaten to tear its people apart.
On his own, Quint can do nothing to help avert the impending doom. But with the help of a band of loyal friends he might just be able to avert disaster.
The Winter Knights is the second book of the Quint Saga - first trilogy in The Edge Chronicles, the internationally best-selling fantasy series, which has featured on the UK and the New York Times best-seller lists and sold more than 3 million copies. There are now 13 titles and four trilogies in the series, but each book is a stand-alone adventure, so you can read The Edge Chronicles in any order you choose.