I have to agree with the people saying Revs; it is really underrated. There's just so much to remember, and like someone said before (I think on page 1), there are so many different events but in the exam you only get tested on 2 or 3. That means you have to know each event really, really well to be able to write on it.
That said, the nature of this subject is very chronological, which is immensely helpful in remembering things.
I personally find literature the hardest so far this year; it's a subject (imo) that really requires depth of thought and subtle, detailed analysis and it's a lot of work to build up those skills.