To describe someone as "ahead of his time" is an over-used cliché. However, in Turing's case, it is appropriate in two ways. Firstly, his ideas took years to work out, and his contemporise did not realise the significance of his research. Secondly and perhaps more importantly, if he had lived in a later era, his complicated personal life would not have attracted the attention of the police, and brought about the early curtailing of the dream.
David Leavitt has written an overdue appraisal of Turing that gives him credit for his successes, rather than ascribe the kudos to others because it was safer to do so. This continues the re-acclimatisation of this pioneer into a place of prominence in two fields - the research background surrounding origins of computing, and the code breaking activities that took place in Bletchley Park during World War II.
It would be untrue to intimate that Turing and his colleagues at Bletchley Park "won the war", but their efforts were nevertheless of huge significance. Leavitt gives a broad overview of the activities, and points the reader to further sources. The account is perhaps romanticised, with the place of pure luck glossed over somewhat, but the scale of the code-breaking operation is realised.
The description of the `Turing machine' is well presented, although not for the faint-hearted as it is necessarily very abstract thinking (again, Turing was ahead of his time). Leavitt successfully weaves Turing into a position both as a man ahead of his time, and as a man of his time (influenced by the Hilbert program in mathematics, and Kurt Gödel's revolution in logical consistency or otherwise). The seeds of what are underlying concepts of the digital age (programmable machines, stored values held digitally, and indeed binary numeric representation) are well presented. The result is to raise the stature of Turing, no longer overshadowed by the likes of John Newman.
With the hindsight of more than 50 years, it is hard to imagine the treatment of Turing by not just those around him, but by `society'. Attitudes to homosexuality have changed beyond recognition, and "things would be different now". Where Leavitt is weak is not leading the reader in regard to Turing's death. However, whether suicide or an accident, Turing's death locked his ideas into a time-box from which they took time to be unpacked. Leavitt helps readers to see that they are TURING's ideas.
Peter Morgan (email@example.com)