In two weeks' time Hughes' book could win the pounds 21,000 Whitbread Book of the Year prize, which he won last year with Tales From Ovid.
The panel of nine judges, chaired by Raymond Seitz, former US ambassador to the UK, said: "In this personal collection Hughes avoids every pitfall - of remorse, self-pity, self-justification - that the subject, his wife's suicide, could have led him into. His account of that relationship seems hewn from granite."
The winner of the award for best novel was Justin Cartwright, a television documentary maker, for his book Leading The Cheers, in which an unemployed man returns to small-town America after living in London and begins to rediscover and question his past life.
First novel winner was Giles Foden for The Last King Of Scotland. The book traces Idi Amin's eight-year dictatorship of Uganda from the fictional perspective of a young Scottish doctor appointed Amin's personal physician.
Amanda Foreman's biography, Georgiana, Duchess Of Devonshire, won the biography award.