The Amber Spyglass (His Dark Materials, Book 3)

From the very start of its very first scene, The Amber Spyglass will set hearts fluttering and minds racing. All we'll say here is that we immediately discover who captured Lyra at the end of The Subtle Knife, though we've yet to discern whether this individual's intent is good, evil, or somewhere in between. We also learn that Will still possesses the blade that allows him to cut between worlds, and has been joined by two winged companions who are determined to escort him to Lord Asriel's mountain redoubt. 

Philip Pullman - The Amber Spyglass
The Amber Spyglass is the third (after The Golden Compass and The Subtle Knife) and final novel in the His Dark Materials series, written by British author Philip Pullman, and published in 2000.
The Amber Spyglass won the 2001 Whitbread Book of the Year award, a prestigious British literature award.
It is also the most controversial book.