Not long ago, I was in the same boat as Kim Bobo, having no idea how prevalent wage theft was.

In the summer of 2001, a lawyer phoned me about an off-the-clock lawsuit she had brought on behalf of several Wal-Mart workers on Long Island. A Wal-Mart worker I interviewed in Suffolk County told me that after her store closed in the evening, she and other employees were sometimes forced to work an extra hour for free, after they had clocked out, to help straighten up the store. That worker also told me the store's managers used to lock the front doors so employees working off the clock couldn't even leave if they wanted to.

Perhaps I was naïve at the time, but I was surprised that managers for a big, respectable company like Wal-Mart would be doing such dastardly things.

Following up on that story I wrote for The New York Times, I started interviewing scores of Wal-Mart workers around the country for other stories, and they told me about the many permutations of off the clock work they were forced to engage in - working for an hour before clocking in, working through their lunch hour without being paid for it, being ordered to work three or four hours after they clocked out to finish a lengthy project, being required to participate in Wal-Mart fashion shows on Saturday without being paid for it.

And then several Wal-Mart employees, including some managers, told me about another shameful practice - managers would "shave hours," meaning they would go into the computer and erase hours that someone had worked. This means that through some sleight of hand a manager might change time records so that an employee who worked 45 hours might get paid for only 40 hours, thus saving the store time-and-a-half for overtime.

Soon I discovered that such illegal practices also occurred at other well-known companies, including Toys R Us, Pep Boys and Taco Bell. In my book, The Big Squeeze, I write about an Air Force veteran who told me that managers shaved employee hours at three well-known companies in a row where he worked - Toys R Us, Family Dollar and Rentway. Shocking stuff.

It is encouraging that Wal-Mart top executives say they are trying their best to stop off-the-clock work, shaving hours and other forms of wage theft. Wal-Mart's top executives say they have made it clear to managers and employees alike that off-the-clock work will not be tolerated. But some Wal-Mart store managers and assistant managers say the pressures to minimize their spending on payroll are so immense that they feel huge temptations and pressures to cut corners by -- you guessed it -- having employees work off the clock. As part of its effort to show the world that it has put these ugly practices behind it, Wal-Mart agreed in December to pay more than $352 million to settle 63 lawsuits over off the clock work and failing to give required breaks. I'm sure that Kim Bobo, like me, wonders whether some, indeed many, Wal-Mart employees are still being forced armed into working off the clock.

The workers of the nation, especially low-wage ones, should thank Kim Bobo for writing Wage Theft because it shines a spotlight on a large and largely ignored problem. Let's hope that Kim's book will be a call to action and tougher enforcement not just by the federal Department of Labor, but by state labor departments from coast to coast.

As Justice Louis Brandeis said, "Sunlight is the best disinfectant."