The annual award was presented in a ceremony in London
A book about censorship has won this year's Theatre Book Prize.
Steve Nicholson's The Censorship of British Drama 1900-1968, published by University of Exeter Press, was hailed by this year's judges as 'the final volume of a terrific and important series'.
Nicholson is professor in Twentieth Century and Contemporary Theatre at the University of Sheffield. He was presented the prize at the Theatre Royal Drury Lane by actress Sian Phillips. His book features some of the key dramatic figures of the twentieth century in a study based on files from the Lord Chamberlain's Office.
Judge Colin Chambers said: "Nicholson delivers his original research into the practice of theatre with characteristic enthusiasm. His detailed account of how theatre and the society it reflects interact is seen through the prism of censorship."
The other judges were Sam Walters (founding artistic director of The Orange Tree Theatre) and Sarah Hemming (Financial Times).
Other titles shortlisted include Howard Barker's Theatre: Wrestling with Catastophe edited by James Reynolds and Andy W Smith, 1606 William Shakespeare and the Year of Lear by James Shapiro and John Osborne – 'anger is not about…' by Peter Whitebrook.