The Stranger's Child, a 700-page novel which took Hollinghust four years to write, follows three generations of the same family from 1913 to 2008.
Among its themes are the evolution of British society, class relations and homosexuality, all recurring subjects in Hollinghurst's work, although he rejects the lable of "gay author" as too restrictive.
Judged as having "strong, perhaps unassailable claim to be the best English novelist working today" by one reviewer, Hollinghust is admired both for his style and his content and has won the Somerset Maugham prize for The Swimming Pool Library (1988) and the Booker for The Line of Beauty (2005).
Mortier won the essary prize for Psaumes balbutiés, Livre des heures de ma mère (Stammered psalms, my mother's book of hours), a description of his mother's decline into senility in poetic fragments.
The best foreign book prize was first awarded in 1948 to 18th-century Scottish writer James Hogg's Confessions of a Justified Sinner.
Last year's winner was The Retrospective by Israeli writer Avraham Yehoshua.