The first handbook gave you the conceptual framework: the statistics, the priming phase, the basic gambit structure, the psychological substrate of throw selection. The second volume is for people who've already internalized that material and are looking for the next level of competitive development.
The major addition is the extended treatment of opponent modeling across multi-match tournament play. A single match against an unfamiliar opponent is mostly pattern reading. A second match against the same opponent, who has also been reading you, is a meta-game: both of you have incomplete models of each other, both models are updating in real time, and both of you know the other person is updating. The strategic question is not just what to throw but how much of your actual strategy to reveal in rounds where the outcome might not matter as much as what you teach your opponent about your tendencies.
The volume also covers the specific problems of team competition, which has different dynamics than individual play. Team RPS matches require coordination without communication, which produces a different kind of pre-match preparation.
Tournament stories from the competitive era anchor the abstract strategic material in documented outcomes. The 2003 World Championship in Toronto, the European circuits of the mid-2000s, the specific matches that produced famous upsets — these are the competitive record that the strategic framework is built to explain.
The handbook series is the most complete documentation of Rock Paper Scissors as a serious competitive discipline. Both volumes belong in the collection of anyone who wants to understand the game past the surface.