The most important point is to be aware that this guide by Ryan & Huth is an introduction to logic in computer science FOR INGENEERS/COMPUTER SCIENTISTS, NOT for logicians.
In fact, the authors spend a lot of time on well-known basic notions of propositional and predicate logic, but actually they do the opposite with other arguments, like grammars and authomata theory, which are instead widely unknown between beginner graduate students of logic.
But consider now to ignore the unpleasant disposition of arguments: a general sensation of mess remains. In fact, concepts are explained as in a novel, with a lot of natural language, entailing a great difficulty in separating what is really important from what is only a corollary. It is almost impossible to skim on the text looking for a particular definition or theorem, becouse of this aspect.
I had a quite bad feeling with this book; for this reason I discourage its reading and studying.