If you want to know about Franz Anton Mesmer, there aren't too many places to go. No satisfactory biography exists in English, and most of the material published on him tends to be of the flaky New Age variety. A recent film of his life (scripted by Dennis Potter, starring Alan Rickman) was never distributed, thanks to a nervy legal dispute between its makers and its backers. All of which makes it rather frustrating that Alison Winter's Mesmerized assumes that its readers are already au fait with the man and his works. Mesmer fails to make an appearance in her book, even as a bit player. You won't hear about how he got his doctorate for a plagiarised dissertation on how the …