If this book were a car, its selling would long have been forbidden! The "typos and corrections" offered by Carl E. Walsh's homepage have by now reached 10 pages. Chapter 6.5 "A Basic Open-Economy Model" has this way been completely revised by the maître. So, in case you are determined to read this book, start with a download of those typos and corrections! The publisher does not give the slightest hint of this problem within the book (Maybe, because the standard "errata-note" would have become an "errata-booklet"). This is really annoying, since you may lose a lot of time by trying to understand mathematical derivations, which are simply wrong. Weak consolation: the "typos and corrections" of Michael Woodford's supposed to be classic "Interest and Prices" sum up by now of 8 pages (Or should we say 38 pages, since "certain equations" of Woodford's chapter 5 are corrected in a separate paper? Unfortunately, I'm not kidding). However, Walsh's book does also suffer from contents-related problems: Throughout the book he derives all results based on the social planner solution of his models. He never even discusses the problem of this approach in the presence of the "wedge of inefficiency" that the usage of money can introduce in such models (Lucas, 1987, Models of Business Cycles). So after having yourself worked through Walsh's book and his typos and corrections, you cannot be sure that the conclusions and policy recommendations he draws will also hold for the market solution of his models.
Walsh's Monetary Theory and Policy was a core book in my studies on Monetary economics at uni (actually the older version) and I have to agree with Ludovico, it has plenty of typos. Unfortunately this is largely due to shoddy editorial work than Walsh's lack of understanding ofthe English language. My problem is that the book lacks direction and often when reading it you will find yourself in a cycle of weak and inconclusive arguments. This starts from chapter 1 when he touches on the relationship between money, output and inflation. For a beginner it is easy to get lost in vast science of monetary policy. But Walsh does not make this any easier. That said I really like the practical policy elements in monetary policy and the book does a good job of explaining the history of the Federal Reserve and its experimentation with various instruments. You just feel the book was written in a rush and some of the more complex topics could do with a little work. Sorry Walsh.
My theory on why the editing of this book is so bad is thus: they knew that it would only be read by students who didn't want to use wikipedia in the library in the early hours of the morning. As a history student I found Bofingers book explained ideas in a better way.