As with earlier volumes, McCloud sets out to survey the unknowably vast corpus of things that can justifiably be called both "American" and "comics" and stretches both to interesting and productive lengths.
In addition to many of the usual suspects (Los Bros Hernandez, Chris Ware), McCloud takes us on a deep scrape through the best of webcomics, including our own Ed Piskor's Brain Rot: Hip Hop Family Tree, as well as adventure comics (I was delighted to find both Sailor Twain and Saga here), superheros, memoir, and some of the strangest, most evocative storytelling I've ever read, in a pair of sections called "Even Stranger Adventures" and "The Kuiper Belt." (Here's a full table of contents)
McCloud opens each section with a sprightly, warm, fascinating essay that strikes a perfect balance of industry insight and artistic commentary, and the whole book opens with an exhortation not to skim, but to read it in order because there's a progression here. I read it in order, and I certainly felt like I was traversing a smooth kind of gradient into the field.
If you're a casual comics enthusiast like me — someone who reads a lot of comics, but doesn't follow the industry or try to be comprehensive — then this is just the volume to pick up. I found several comics here that I have since sought out and read avidly, notably Richard Thompson's Cul de Sac, a worthy successor to Calvin and Hobbes that actually ceased publication during Best American Comics's survey period due to the creator's declining health (how did I miss this one?).