Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This book has very useful swimming workouts

I am a masters swimmer. I bought this book several years ago. However, only recently I realized I needed to improve my swimming times, and I do not have a coach. I have been preparing workouts based on this book, and I am beginning to see my swimming times dropping consistently. The workouts provide an excellent combination of stroke work and kicking drills, and it is very easy to follow. The workouts are very long, and the pool where I work out has schedule limitations. Therefore, I have been creating my own workouts based on this book, and I have been obtaining excellent results. I have been splitting the workouts in two, and when my schedule allows it, I have been using complete workouts. I just dropped 2 seconds in my 200 backstroke, 15 seconds in my 100 fly, and 21 seconds in my 200 IM at the Long course nationals in Ft. Lauderdale.