A gorgeous cookbook with a huge photo for each recipe. The book itself is also huge and—as it's printed on glossy paper—heavy too. Because it's America's Test Kitchen, you know everything's going to turn out, even if they can get a bit fussy at times with all their weird steps, and if you balk, the introduction to each recipe will convince you that all the weird steps are necessary.
There's an entire chapter on brownies, as well as Christmas cookies, drop cookies, slice and bake, sandwich cookies, rolled cookies, bar cookies, no-bake cookies and candies, fancy cookies, and gluten-free cookies. But! That last chapter is pretty short, with only ten recipes, and they still want you to use their custom gluten-free flour blend. Or, they'll tell you how much to use of the gluten-free flour blends from King Arthur, Betty Crocker, and Bob's Red Mill. I don't think there's anything in here that isn't in their two gluten-free cookbooks, but there is a nice note at the beginning of the chapter with a list of naturally gluten-free cookies elsewhere in the book, like meringues, almond macaroons, and chocolate spice cookies.
Measurements are in U.S. volume and ounces, almost every recipe has storage advice, the opening introduction is an excellent resource, there are illustrated technique workshops sprinkled throughout, and the index is comprehensive.