Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A sound textbook for dojo practice

I found very useful to complement my karate training from the master himself. Since karate is transfered from master to student, each one adds their own variation and over the years diverts from the source. Having a book true to it is very useful to understand many things we practice over and over.The book is very clear and easy to follow, helping to correct style and stances.