The latest Liverpool Biennial, titled The Unexpected Guest, explores the underwhelming theme of hospitality. It's a city-wide catch-all including 242 artists in 27 locations: rude words by Gilbert & George, Mona Hatoum in the Cunard Building, the sci-fi work of Anthony McCall and the brilliantly voyeuristic photographs of Kohei Yoshiyuki. Various venues, Liverpool, 15 September to 25 November.