Readers curious about food have been able to deepen their knowledge exponentially over the last decade. They know how bad fast food is (thanks to Eric Schlosser), understand the complexities of food production (thanks to Michael Pollan), and know how hard it is to work in a kitchen (thanks to Bill Bryson). There are shelves upon shelves of books about how, why and what we eat by restaurateurs, farmers, chefs and even moonlighting novelists.

Add to the mix Tracie McMillan, who found employment at the bottom of our nation’s food chain and wrote about it in a book that’s a foodie version of Barbara Ehrenreich’s Nickel and Dimed: On (Not) Getting by in America. McMillan is an award-winning journalist whose work has focused on poverty.

A white woman in her 30s with a college degree, she is an unusual figure looking for work in the fields of California’s Central Valley. When asked, she makes vague allusions to wanting to leave problems behind, be outside and stay away from people. Though she wields vast knowledge about the conditions faced by agricultural workers, she serves as an everywoman, an understandable lens on an unseen world.

In this way, the book is vital. She has the writing skills to bear witness, the research background to provide context, and the courage to take on the task. The challenge is constructed: For each effort — farms in California, Wal-Marts in Michigan, Applebee’s in New York — she serves a two-month stint. She begins her project with a month’s savings, and when her car’s radiator fails, or a check amount is less than expected, like many other Americans she taps a credit card to make ends meet.

Each section begins by outlining how much she earned producing food and how much she spent on what she ate. In the fields, she spent 25 percent of her $10,588 annualized salary; at Wal-Mart, 17.2 percent of $11,487; at Applebee’s, 13.5 percent of $12,845. What those numbers don’t reveal is how much she depended on the kindness of strangers.

McMillan gets hired to pick grapes, sort peaches and harvest garlic. She lands her first job with the help of a sympathetic neighbor, who brings her along when the work is scarce in a mini-business of selling breakfast to other workers (McMillan provides the soda). Acquaintances share surplus food from the fields. A woman unloads a bounty from the throwaway bins at Trader Joe’s. A Michigan landlord stocks the kitchen and rewards on-time rent with pizza; in two houses where she rents rooms, the landlords regularly feed her home-cooked meals.

The fact that these actions are recorded but seem to go unrewarded by her becomes one of the increasingly uncomfortable elements of the book. These are, after all, families for whom it makes sense to displace a teenage son from his bedroom for the $300 McMillan will pay that month; how can she rapturously write of the seafood soup without offering to stock the fridge once in a while? Perhaps these transactions happened but were too intimate to be recorded.

Also missing is intimacy. McMillan is excellent at describing the surface of things — where to stand to sort just-picked peaches, how many training videos a new Wal-Mart staffer will watch — but she omits the feel of things. If her muscles hurt after that first day in the fields, if she was bored stocking shelves all night, we don’t know it.