.. hasn't been following the syllabus how?
in order of dot points, ie chronologically, or just, making it up as they go?
first thing, talk to your ah teacher and let them know how youre feeling, if youre concerned about something, etc, etc.
secondly, it depends on the electives youre taking.
over all, the excell book is good for quick revision, but not much else.
for pompeii, i find the estelle lazer book (cant remember what its called) very very good.
i can only speak for greece at the moment, but pamela bradlee is good in terms of sources and detail. very dry though.