GCSE Bitesize: slanted directly towards the skills needed for the GCSE exam
Shmoop guide: take a look at the Why should I care? section on the first page. These guides are always written in a witty and irreverent style, so be careful not to take some of the comments as deadly serious. I’m not sure how an examiner would respond to the description of the dead parachutist dropping in “Mary Poppins” style!
Sparknotes: the usual Sparknotes comprehensive study guide with a good summary on themes and symbols.