I'll nominate
The Golden Compass (
The Northern Lights in the UK), the first volume in the
His Dark Materials trilogy by Philip Pullman.
Sometimes banned or contested because of a perceived anti-religion bias, though that's almost entirely in the later books. It's sort of the anti-Narnia. (Plus it has armored bears! I loved the armored bears.
)
Amazon US:
http://www.amazon.com/Golden-Compass...=UTF8&qid=&sr=
Amazon UK:
http://www.amazon.co.uk/Northern-Lig...orthern+lights
Edit to add summary:
Spoiler:
Lyra's life is already sufficiently interesting for a novel before she eavesdrops on a presentation by her uncle Lord Asriel to his colleagues in the Jordan College faculty, Oxford. The college, famed for its leadership in experimental theology, is funding Lord Asriel's research into the heretical possibility of the existence of worlds unlike Lyra's own, where everyone is born with a familiar animal companion, magic of a kind works, the Tartars are threatening to overrun Muscovy, and the Pope is a puritanical Protestant. Set in an England familiar and strange, Philip Pullman's lively, taut story is a must-read and re-read for fantasy lovers of all ages. The world-building is outstanding, from the subtle hints of the 1898 Tokay to odd quirks of language to the panserbjorne, while determined, clever Lyra is strongly reminiscent of Joan Aiken's Dido Twite.
A few years ago he was the second most banned or restricted author in the U.S.