Kroeger’s point with all this historical research is to put undercover reporting on a continuum, from no-lie investigations on one end to Mirage-style theatrics on the other. But she gives what I consider to be an over-expansive definition of undercover reporting. Almost any project that has relied on any combination of deception and subterfuge to expose a story of public importance seems to qualify. For instance, her lead example is the 2007 Washington Post series by Anne Hull and Dana Priest about the deplorable treatment of patients at Walter Reed Army Medical Center. As Kroeger acknowledges, Hull and Priest never assumed false identities in their reporting. They told no lies and donned no disguises. Yes, they shunned personnel who might ask them nosy questions, and they didn’t ask officials for permission to report at the hospital. But if such evasive maneuvers equal “undercover reporting,” I would hypothesize that 75 percent of all working reporters have at one time or another in their career gone “undercover,” too.

Kroeger juxtaposes the Hull and Priest investigation (and “no-lie” investigations like it) with the work of aggressive journalistic liars because she finds unity in the two techniques, and wants to explore “whether there is really a difference for a journalist between not ever telling a lie—emphasis on the word telling, because lies, to qualify as lies, are verbalized—and the deliberate projection of a false impression with the clear intention to mislead, to deceive.”

But placing the Walter Reed investigation inside the same journalistic genus as the Mirage series constitutes a grievous taxonomical error. The “deliberate projection of a false impression” is something reporters do almost daily. When an official inadvertently spills the beans during an interview, the smart reporter suppresses his excitement and caps his pen in hopes that the official will dig himself in deeper. Such deliberate projections, by the way, must rank among the most common human activities. Parents scowl at their children to make them behave when they’re really not angry; buyers feign nonchalance to convince sellers to lower their prices; and so on.

In my mind, there is a world of difference between the two undercover genres. Compare, for example, the famous workplace investigations conducted by Tony Horwitz, Charlie LeDuff, and Barbara Ehrenreich, which Kroeger neatly summarizes, and the works of Silverstein, the Chicago Sun-Times, and James O’Keefe and Hannah Giles, the BigGovernment.com contributors who pretended to be a pimp and prostitute in order to embarrass the advocacy group ACORN.

When Horwitz and LeDuff went to work at slaughterhouses for The Wall Street Journal and The New York Times, respectively, and Ehrenreich took menial jobs for her book about the working poor (Nickel and Dimed), the lies they told were de minimis. Ehrenreich, for example, omitted from job applications parts of her distinguished academic record. They created no new scenarios by their actions—they merely slipstreamed themselves into a story already in progress. Once there, they did little or nothing to contaminate the reportorial soil.

Silverstein, the Sun-Times, and O’Keefe, meanwhile, didn’t just contaminate the soil, they created it by telling their fictions. They then invited people from K Street, the Chicago bureaucracy, and ACORN to join the casts of their improvisation. The difference is between writing about a world that already exists, and conjuring one to embarrass the potentially guilty, a distinction Kroeger seems not to want to accept.

I would be misrepresenting Kroeger if I implied that she defends every lying reporter ever to carry out a convoluted sting. In her preface she writes that “at its best, undercover reporting achieves most of the things great journalism means to achieve. At its worst, but no worse than bad journalism in any form, it is not only an embarrassment but can be downright destructive.” I wish she were more judgmental about some of the techniques some reporters use, but Undercover Reporting is not that kind of book. If you are the type who seeks a thumbs-up or thumbs-down on every controversy, Kroeger is not writing for you.

Jack Shafer writes a column about the press and politics for Reuters.