Dont bother reading the ANO just yet - if i were you id get stick into section 1 of MATS. This is far better as alot of the basic course (first 3 months) is built around this section. After the basic course, you will start your chosen route whether that be Area, Approach or Aerodrome, and they all have their own separate sections.
Reading the ANO just now will be a waste of time as most of it wont make sense and it only became clear to me once we started the lessons.
Aircraft characteristics is a good easy place to start, try
www.airliners.net it was use to me. Try and get on as many visits to units as possible - to see what you REALLY want to do.
Anything else PM me.