I finished reading this book just this morning. It's less lengthy than the other books of his I have (and have not yet read: The Omnivore's Dilemma and Botany of Desire). I do look forward to those other books, but I was invigorated by In Defense of Food as it takes an informed activist approach to looking at how and why we eat the way we do, and what "forces" are interested in maintaining that zeitgeist.
The option Pollan counters with is so simple, so logical, so easy (once one gets past some newly acquired habits) that it begs to be adopted. What a relief to drop the mania to look for the newest nutritional study for guidance, the need to be a chemist to figure out what to look for in food labeling.
This fits so well, so hand-in-glove, with some other threads in my life, towards simplicity in structure, toward logic and pragmatism, toward acting upon ideals, toward health, toward gardening expansion. This is a book of substance, but a pretty easy and fast read. Recommended.