Surprisingly informative. These "How to Read" books are often subject to ridiculous tirades and as a result I didn't expect much. I have to note that this book didn't clarify certain elements of poetry sufficiently, at least not for me; notably metre and form. Nevertheless they have always been a weakness for me when it comes to poetry, I also have a feeling I just need to sit down and commit them to memory.
There were digressions in this book not entirely pertaining to how to read poetry, however these chapters can be skimmed over and Eagleton reccomends this. Although I'm not complaining about this at all, they were nice extras in my opinion.
As a final note, if you have doubts about certain elements of poetry try to get this second hand and it might help you out.