Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A bit less than just a reference

Filled with logically structured variations, this book helps in no way to understand the opening. You have to find by yourself.But at least it's a huge reference on a not usual topic. It doesn't include ( like the book on the Grob ) a chapter of complete games, so it makes it a bit less useful than it's counterpart on the Grob by the same author.