Background: This year I'll do another Group Theory course ( Open University M336 ). In the past I have used Mathematica's AbstractAlgebra package but (although visually appealing ) this is no longer sufficient (i.e. listing subgroups of $S_4$ takes ages). So, I want to learn more about GAP. I worked through beginner tutorials that I found via the GAP website. Currently, I am not making much progress with GAP. The reference manual does not help me much at this stage.
Question: What is the best way to self-study GAP? How does one become proficient in GAP? What ( books, tutorials ) should you study?