Instruct: Classify Amazon reviews into positive or negative sentiment
Query: pure garbage

This book is total garbage. I have a BS in EE and wanted to learn more about switching power supply design. This book is useless. Instead of explaining the general operation of boost and buck converters with english words, Krein uses these convoluted switching matrices. It's like the following: here's a circuit, and here's its switching matrix, on to the next cicuit. Not insightful in the least bit. He should spend more time explaining with English words what is going on in a circuit instead of just throwing a uninsighful matrix at you. It's a typical professor/academic book: too many irrelevant details and not enough on the basics.