if u want to study for atpl i'll suggest u oxford book for nav, radio and instrument only for theory part....like if u want to know the topic but if u want to just clear the xam then just go through keith williams question bank.......
as far as i know that radio aids question bank is not available in keith williams so have to study radio questions from oxford only or u have to study the book......
and for met read the I C JOSHI and do all the question which is given at the end of the chap.......
that will clear ur atpl........