Not worth the paper it's printed on.
Restall presents an awkward introduction to formal logic. Explanations are convoluted and a chore to disseminate from the text. The book features several errors in both the main text and exercises which can only do harm to the reader. Explanations come across as muddled intertwined with a very casual and imprecise literary style. If you are looking for a straight forward and clear introduction to propositional and first order logic, look elsewhere.