Mind Mapping is a form of activation. The big difference being that Mind Mapping involves using pictures, text, lines, colors and such to sort of sum up the book and what it's about. Remember, the mind see's words in pictures and pictures as they say are worth a thousand words!!!
I know that when I wish to 'refresh' my PR techniques ... I quickly glance at the mind map and voila ... the reading experience is instantly refreshed in my memory! Or at least this is or has been my experience.
But mind maps are great for books when you revisit them months/years later ... it a great refresher!
MInd maps may take time to do ... but if your goal is to remember or comprehend instantly what the book is about ... mind mapping may be what you need.
Oooh, there I go rambling again, do you need to use mind mapping ... by all means the decision is up to you. Remember, there are other forms of activation at your disposal. The beauty is ... you get to choose which one your comfortable with!!!