Instruct: Classify the given Amazon review as either positive or negative.
Query: congratulations

Words fail me to congratulate Harris for the splendid work he has done. The four books offer a large selection of secrets and techniques for studious billards players to explore. Putting all those systems and techniques into words, must have been pioneering !!! The greatest billiards players will nearly never reveal their secrets, unless one's willing to pay for expensive private lessons. People like Harris are very rare in the world of billiards