Instruct: Classify Amazon reviews into positive or negative sentiment
Query: The only book for advanced GR

Although it seems to be a general relativity book, this is actually an excellent book for learning advanced mathematics. The sections on differential geometry and spinor analysis rival any of the dedicated textbooks on these subjects. This is also the only book to give a clear and concise introduction to tetrads and the Newman-Penrose formalism of general relativity.This book is a must for any serious physicist.