I am a huge fan of the York Notes Advanced series. I used them when I was studying for my A-levels and as a recently qualified teacher I now plug them as often as I can. They are detailed, critical, and fantastically well researched; it is really quite unusual for this sort of book to come with so many recommendations for further reading. The chapter-by-chapter summaries are useful to have open as you read through the book for the first or second time and the in-depth 'extended commentaries' are an excellent model of focused close reading. Buy it!