Well, this is pretty dense in a way that books usually aren't these days. Not dense in a Frenchified theory way, and not dense in a flowery language kind of way. Just conceptually dense. Which is fine, but not all of the concepts are useful. Density aside, the first two essays - on historical criticism and 'symbols,' (which for Frye doesn't really mean, well, symbol) - are pretty good, if overly schematic. The third essay is horrific. Really, you just need a diagram for it, but we get over 100 pages instead. The fourth essay, on genres, is occasionally interesting but also too schematic and way too long. I'd stick to the introduction and first two essays, and skim the rest.
One thing that's odd is that people say this seems 'dated' thanks to Marxist or feminist or postcolonial theory, or deconstruction. Not really, though. Frye's aware of all those trends already in 1957 (not counting postco, I guess); and his work isn't dated by deconstruction. It's just the opposite side, handily summarised in Harold Bloom's (awful) foreword: for Bloom and his ilk, literature is all about indeterminacy, and more or less a brawl among self-loathing geniuses. For Frye, literature is a "cooperative enterprise," part of the attempt to make life better for ourselves. Not dated, then, but one side of an ongoing argument. Frankly, I hope Frye's side wins. Then there'll be no need to re-read this book.