The book mainly talks about "claims" which is basically any unit of information you hear from others, and "arguments" which is a special kind of claim usually backed by other claims. The authors provide a very practical approach towards evaluating claims and arguments we witness in our day to day lives.
For instance, as an engineer I read/hear comparative claims like "Because of the feature X, product Y has grown from A # of users to B # of users in 5 years" everyday and I conduct experiments which involve understanding and rectifying sampling biases. It's very common to find arguments that beg the question, like arguments which pretty much reduce to "We should do this, because we should do this". This book was very useful in understanding recurring patterns in arguments, and provides lots of exercises to internalize those ideas.