The book addresses various features of programming languages from a mathematical viewpoint. It discusses semantics of things from simple imperative language to failure to concurrency issues using channel based and shared memory concepts. It is a good book to get an idea about most of this concepts if you do away with the math involved. If you can swallow the math you will be able to come up with semantics for various systems fairly quickly. I have read the Winskel's book on semantics. I feel this book is a touch away from all the math stuff compared to Winskel's book. It would be better to refer to Winskels book after this book.