This is a difficult thing to review because it's not a gestalt in any sense of the word. It is a series of essays, taken from various places at different points in Glück's career, divided into four sections, which don't really have overarching themes (at least definitive and obvious ones (excepting the third)). Some of them aren't really even about poetry. (Some barely talk about the writing life.) That doesn't seem overly difficult, does it? Sounds like an awful book. Well, no, because I haven't introduced the difficulty, which is that the essays are brilliant. I use this word sparingly, and tend to polish it up before I gingerly, oh-so-delicately apply it to something; and her essays deserve the word, and certain ones in particular. I won't bother you with unities and summations here, because parsing her essays is your job, but American Originality, American Narcissism, Ersatz Thought (especially this one), and Fear of Happiness should all be firmly ensconced in the greater American essayist tradition. They are inciteful, caustic, humbling, and enlightening, and they give one the sense that literature, well, it goes rather deep (which of course it does). Glück may be a literary genius. Surely we know this from her Nobel Prize last year (this I say only slightly tongue-in-cheek), but her essays truly astounded me. I cannot give them high enough praise; her skill as analyst and stylist is on display page after page. One can pick this book up at random and find something delightful in each paragraph.
This might be very odd to say, but I find her essays better than her poetry, at least that which I've read. This is in part because I can tell she has a hyperanalytic mind, and something about the essay suits that mental faculty better than most poems (not to say that this is impossible. Look at Pope). Overall, perhaps don't buy the book, but definitely, definitely, definitely, you must find those essays.