Crossover genre fiction mixes two normally discrete genres, and ideally combines the pleasures of both. Jack Reacher, until immediately before the opening of the novel in which he first appeared, had been a professional soldier in the post-Vietnam American Army, a major of military police. Lee Child's conceit is that military police are immensely formidable men, since they are trained to deal violently with men who are trained soldiers, i.e. specialists in violence. For all I know, this may even be true-a mutual friend once watched a strikingly sweet-tempered, late-middle aged, overweight and severely asthmatic acquaintance effortlessly break the arm of a young, large, fit and very sudden assailant, at which point the observer recalled that the pudgy and ageing asthmatic had been a Marine military policeman in Vietnam. Then again, it may not always be true, since I have never heard a combat veteran of the Second World War express awe at the martial prowess of MPs. Whether or not it is true in fact, it works in fiction, where Lee Child's Jack Reacher, like MacDonald's Travis McGee, is both very large and startlingly proficient at violence. Unlike McGee's, Reacher's feats are all explained, in some detail, as the result of specialized military training. The point of these episodes is that unlike the feats of former soldiers in older thrillers, Reacher's prowess is imagined to be impossible for anyone not very extensively trained as a long-service professional soldier. The formula has been amazingly successful. Child seems to have intuited that women as well as men would enjoy reading about an ex-military superman, and he was, at least until recently, dead on.

In Reacher's first appearance, his enemies were not themselves possessed of military training. In subsequent novels some of the villains were soldiers — the logic of the premise may even have required that turn, since if soldiers are invariably vastly more formidable than any civilian, Jack Reacher novels would otherwise have been as suspenseful as Superman stories would have been in a world without Kryptonite. But why were the novels so remarkably satisfying to so many readers? Probably because in consequence of his being an ex-soldier who had spent his entire life in an around the army, Reacher was imagined to be indifferent to money, ascetic, incorruptible, wholly fearless, and invariably given to acts of solidarity and honour that Child implied were at least improbable in a civilian. These qualities were depicted as almost uniquely military virtues, understandably alluring (and plausible) to a readership generally unacquainted with soldiers or armies. Reacher was an immigrant from a world separated from, and morally preferable to, 1990s America. Lee Child seemed to greatly admire the American military, not an attitude too frequently expressed in 1990s British or American publishing circles or film industries, which may explain why the Army was generally ignored in much of 1990s popular culture. It was a bold bet, and in commercial terms, anyway, a vastly successful one. Nothing To Lose, the most recent novel, is Lee Child's first novel to make sustained reference to the Iraq War. The novel's villains profit from that war, while the serving soldiers in the novel are either peripheral to the plot, or else shattered victims of the war. As has happened before in the series, the novel's serious action begins with Reacher wandering into a desolate small American town in the middle of nowhere, where the local authorities are guilty of at least indifference to brutality and malfeasance. The novel ends with Reacher solving a series of mysteries after repeatedly beating the villains like drums. In this case, however, there is a crucial change in the plot, and if one opens the book expecting the pleasures provided by its eleven predecessors, it may bitterly disappoint. The chief villain is a Rightist evangelical who embodies many of the sins that authors, publishers and film-makers fairly regularly discern in American elites: in addition to being a (Christian) religious fanatic, the villain is also very rich, traffics in deadly toxic wastes, tyrannizes over the whole of a community with no opposition of any kind, and is thick as thieves with the military-industrial complex. Readers cued by some recent thrillers, who may expect to discover yet again that the specter of terrorists armed with weapons of mass destruction has provoked the American Right into an overreaction more dangerous than any terrorist armed with WMD, will in fact be disappointed, but only because in Nothing To Lose the terrorist armed with WMD is himself on the American Right. This cunning twist spares the reader from considering the possibility that dreadful events have forced tragic choices on the authorities, who have under that pressure made comprehensible if sometimes ghastly mistakes.

The Iraq war, here imagined as pretty squalid, is also implied to be a grotesque and irredeemable blunder, and the soldiers who have served in it are more to be pitied and mourned than celebrated or even much admired. This attitude is in some ways retrospectively projected back onto the military that had been celebrated in the earlier novels: the last war worth the sacrifice of soldiers' lives, Reacher at one point explains, was WWII. Lee Child may have suspected that 2008 was not a good year for a mass market thriller directed at a civilian audience to idolize the American Army, and thus sought to update his brand. If so, the cost of his move may be pretty steep. On this new vision of the American Army, the military virtues are presumably obsolete, and soldiers are not immensely formidable, but merely horrifically vulnerable. This seems a very risky move for a man who has made a fortune celebrating the prowess of American soldiers for an audience apparently very innocent of both their trade and its history.

Reacher remains an omni-competent killer and brawler, but the world from which he has emigrated into ours is no longer one his inventor is prepared to depict as worthy of our fascination, and is a instead a world of exploitation, deceit and defeat, populated chiefly by victims. Reacher, who was an original because of his inventor's enthusiastic adumbration of an American military subculture, has been made less plausible, because he is now too unique a figure. His prowess and remarkable physical size remains, but he has nonetheless become smaller. Child's imagined world, alas, is no longer too appealing a holiday from ours.