This book is very good. It is easy to see why it is the standard undergrad textbook (along with sweet & mazwell). It is clear & concise & gets across points well, often using very good examples.
The book also goes into depth. It is well structured & well headed throughout, so a student can skip certain parts if they are not relevant to their particular course/essay. There is plenty of critical analysis, up-to-date academic criticism of the law and, at the end of most chapters, ideas on reform.
The book starts with general principles of criminal law...Actus Reus, Mens Rea, Strict Liability, General Defences, etc. It then goes on to consider specific offences, such as homicide, assault, criminal damage, theft, etc. It goes into sufficent depth on each one to meet most of the needs of an undergrad student.
Though it would be foolish for a student to use only one book throughout their course, as it is always best to learn from a range of sources, this book is so comprehensive, clear and concise that it can be used as the base for a study of the criminal law. If you only buy one book, make sure it is this one (or the S & M!!), but please do not rely solely on this one book, whatever its merits.