If you dismiss the Discworld novels as the domain of 40-year-old men who still live with their mothers, think again. At his best, Terry Pratchett mixes great dollops of sly Swiftian satire with a jolly good story - and Small Gods is one of his best. The Great God Om (Patrick Barlow) has fallen on hard times. Despite having an entire city devoted to him, no one actually believes in him anymore. And without that oxygen of belief, he is reduced to the ignominious form of a tortoise. Robin Brooks's admirable adaptation keeps the Pratchett wit intact.