Instruct: Classify a given review into positive or negative sentiment.
Query: The only group theory book for the advanced reader.

This book is, I suppose, the most authoritative and comprehensive text on group theory. Text is quite succinct and self-contained, proofs are elegant and rigorous. Only few sections of the first chapter cover undergraduate group theory. Therefore I do not recommend it for the one that would prefer an introductory text rather than a serious reference text. It is also a strong self study text, the example questions are well-chosen and generally demanding. Though its name begins with `A Course...', I think it contains enough material for more than 3 courses, a semester each. It is definitely worth its value, a must for a mathematician's library.