Sir Vidia's Shadow by Paul Theroux (Penguin, £7.99 in UK)

Any one of us, asked to analyse a 30-year friendship, would find it a gruesome business. Why do we stay friends with particular people for years and years while others disappear gently from our lives or tear great holes in them after only a matter of months? In this astoundingly detailed account of Paul Theroux's friendship with V.S. Naipaul, the West Indian-born writer comes across as prissy, racist, paranoid, ungracious and petty. Bludgeoned again and again by examples of Naipaul's unpleasant behaviour, you find yourself wondering why Theroux would write such a merciless book. Was it to get revenge for the sudden, enigmatic ending of the friendship when Naipaul remarried? To hang on to a connection, however tenuous, with a truly famous writer? Or simply for the sake of good copy? Painful to write, no doubt, and certainly painful to read, it's one of the most memorable biographical studies you'll ever come across.