I did the CELTA, I also went and bought the book
2. Learning Teaching Jim Schrivener (Macmillan)
I have it here, what a waste of $45 , never needed it.
However we never used any of them, although my CELTA was all in-class stuff for 4 weeks...or was it 2 weeks intensive ?
Anyways, you definitely won't need all those books.
As mentioned by Gepikfail....grammar (tenses, you won't realise how little you know until you actually have to study it) and phonetics