Contested Will: Who Wrote Shakespeare? by James Shapiro (Faber & Faber, £20) tackles the conspiracy theories surrounding the persistent question of whether Shakespeare really wrote Shakespeare's plays. With verve, authority and humour, Shapiro shows that the "authorship controversy", like all conspiracy theories, depends on a mixture of confirmation bias, pre judice, ignorance and wilful irrationality. He reconstructs the history of the argument that either Francis Bacon or the Earl of Oxford wrote the plays, and shows how they came to be accepted by people who should have known better, including Mark Twain, Henry James and Sigmund Freud. Most of the theories boil down to snobbery: the plays are great, therefore an aristocrat must have written them, rather than "the grubby Stratford man". As Shapiro proves conclusively, the hunt for an alter-Shakespeare involves exactly the kind of pseudo-cryptology that made The Da Vinci Code so popular - and so stupid. He ends with a bravura chapter outlining the case for believing that Shakespeare wrote Shakespeare - a masterful demonstration of the principle of Occam's razor.