Dan Richards’s latest book, Outpost (Canongate), is a sprightly tour of places on the edge — among them the bothy, the writer’s retreat, the fire lookout tower and the lighthouse — and the thresholds they mark, both on the ground and in the head. The author was invited by the excellent Five Books site to name his favourite works of landscape writing. His quirky selection, offered in an interview shortly before Alice Oswald was elected Oxford professor of poetry, includes her Dart, which she herself has described as “a river map of voices, like an aboriginal song line”.