hi buzzc152
unfortunately there are not that many books JAA IR related. Have a look at trevor thom (i believe is No 3) it should contain some interesting info. Also the Aerad "Flight information supplement" is worth to have a look at. Further information is also available on the Aerad "Europe and middle East supplement" quite useful for information related to NDB and VOR ranges.
However, usually FTOs have got their own note for the IR which relates to instrument flying and specific aircraft type management.
Said that if i were you i would try to go to bed and sleep as the training is already quite demanding and good nights sleep are worht as much as good books.
You may also find yourself reading the Bible half way through your training so if you already have not got one you may want to order it and keep it next to your bed
Stay cool and do not overload yourself (easy to say)