After writing nine cookbooks and hosting a PBS cooking show about her own Jewish heritage, Joan Nathan decided to explore the cuisine of other ethnic groups and recent influences on the way we eat (including the Cuisinart and ice cream mix-ins). The result is The New American Cooking (Knopf, 464 pp., $35), a big, colorful new cookbook cum travelogue that she'll be discussing at the Free Library tonight. Although the cookbook is set up traditionally, with recipes grouped in bread, starter and dessert chapters, it's also stuffed with sidebars that explain the origins of newish ingredients like lemongrass, wasabi and portobellos (Nathan credits area residents Maria Venuti Forrest and Don Phillips with bringing those meaty mushrooms to the U.S.) and recipes like morning glory muffins and molten chocolate cake (the latter the result of celebrity chef Jean-Georges Vongerichten taking some chocolate cupcakes out of the oven too early).

On the phone from a Kansas City bookstore stop, Nathan said she will tell the Free Library audience about some of her adventures while researching the book, including harvesting wild rice with Ojibwe Indians in Minnesota, attending a 4 a.m. fish auction in Honolulu and "eye-opening" visits with huge families of Cambodian, Ecuadorean and Gambian immigrants to feast on exotic soup, fish casserole and grilled chicken dishes, respectively. (Few Philadelphians made the book's final cuts, a fact Nathan, of Washington, D.C., blames on her lack of familiarity with our city and on her deliberate attempt to seek out new immigrants "in out-of-the-way places to show that they are everywhere, not just in the big cities.") She'll also be waxing philosophical about "the state of American cooking today and where it's going."

Although Nathan says she is "not blind" to fast food, agribusiness and statistics that say people are cooking less and know less about how to do it, these sad facts are not the focus of her book or her interest. She prefers, instead, to talk about the rise of farmer's markets (she says they've increased tenfold in as many years) and the hipster Persian restaurant in L.A. she patronized recently along with a bunch of young, upwardly mobile Persians.

"You wouldn't have seen Italians in an Italian restaurant 50 years ago because the Italians would want to be Americanized," Nathan says. The switch, Nathan suggests, says something positive about newer American immigrant self-esteem as well as the authenticity of the food in the ethnic restaurants where Americans are doing more and more of their eating.

Joan Nathan speaks Thu., Dec. 1, 7 p.m., free, Free Library of Philadelphia, 19th and Vine sts., 215-567-4341, www.library.phila.gov.