I also started my atpls in January 13. Working 6 days a week, and studying in the evening is a tuff going for me. Half thinking of leaving my job so i could put more effort into studies.
I find Gen nav interesting , but hard. Lots of formulas, techniques,etc that can be easily mixed up or forgotten if your not keeping up with it.
Im on my 4th book now, hope to sit exams soon and hopefully find more time to get this done and dusted.