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The Ekumen by Ursula K. Le Guin
Worlds of Exile and IllusionWorlds of Exile and Illusion by Ursula K. Le Guin
Buy new: £8.43 / Used from: £4.55
Contains three early stories - Rocannon's World, Planet of Exile and City of Illusion - that are somewhat out of synch with the later books.
The Left Hand of DarknessThe Left Hand of Darkness by Ursula Le Guin
Buy new: £4.97 / Used from: £2.91
The best book ever about friendship despite great cultural differences.
The Dispossessed: An Ambiguous UtopiaThe Dispossessed: An Ambiguous Utopia by Ursula K. Le Guin
Buy used from: £1.79
Interesting story about how anarchy might work (and its problems).
Four Ways to ForgivenessFour Ways to Forgiveness by Ursula K. Le Guin
Buy used from: £1.54
Four adorable stories about love in a culture trying to rid itself of slavery.
The Telling (Gollancz S.F.)The Telling (Gollancz S.F.) by Ursula Le Guin
Buy used from: £0.01
Wonderful tale about an old culture threatened by a mindless technological revolution.