I find it hard to understand why Nibbana would be the cessation of two trilakkhanas (anicca and dukkha) but not of anatta, which would remain valid until the end. 
I have always felt that these three truths should be understood as a whole. Impernanence being a source of dukkha for the one who clings to it (who makes it his own).
All composed things being impermanent (anicca), impermanence being unsatisfactory (dukkha), these things can not be considered as oneself (anatta).
If you have any good books to recommend on anatta, I’ll take them! I’ve been told to look into Nagarjuna… Maybe the problem is that I wonder too much about what Nibbana is, almost thinking in terms of substance, instead of what it is not (sunyata).