Personally, I find that images or drawing stuff helps me both learn and memorise things.
Like take for example, a large book with lots of text. If I read through it, I will probably remember 5 % at most. But if I read a page or a chapter and then try to convert what I've understood into a mindmap then its usually with me for good. (think big circle, lots of other things coming out of it). If you do it in such a way that you break it down and thereby simplify it you should have no problem remembering the simplified structure in your head and the rest will come.
Oh and I don't think anyone can remember things long-term if they don't 'freshen up' on them every now and then so I wouldn't be surprised if you're not remembering this stuff 5 months on.