This is a very powerful book. It's a first-hand account of how Orwell found himself volunteering for an anti-Fascist brigade, and how utterly disillusioning the whole experience was, as the fractious anti-Fascists wasted enormous amounts of energy fighting each other instead of the real enemy. There are relevant lessons for any political campaign today (certainly I see the same tendencies in the environmental movement), and it also does a lot to illuminate where he was coming from with Animal Farm and 1984. Having studied these at school I was left under the impression that Orwell was a rather pro-establishment writer, but reading his non-fiction makes it clear that he was a strong ideological Socialist, and his critiques of Stalinism have all the bitterness of someone seeing his own ideals betrayed.