Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This is the definitive book to own

By far and away, if you need a price guide to sheet music values, this is a "must have" book. Warning, it doesn't have every single piece ever printed, but it must have 95% of them. With the changing economy over the years, you can't take the prices as realistic, but it will give you an idea of relative value. There is no current substitute for this book; it's the best reference book available - I would suggest to buy it without hesitation.