A splendid article by Toby Lichtig in the TLS looks at various reincarnations/re-examinations of the great detective (with very pithy remarks saved for the latest film). Try the following:
Michael Dirda On Conan Doyle 232pp. Princeton University Press.
John O’Connell The Baskerville Legacy. A confession 190pp. Short Books. £9.99.
Anthony Horowitz The House of Silk 294pp. Orion. £18.99.