Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Excellent guide, somewhat difficult to get used to

The Sanford Guide is a well-known pocket guide that every medical professional should have, from third year medical students on up. It is concise and easy to carry around. My only complaint is that its use is not entirely intuitive and takes time to get used to. It updates yearly so it's guaranteed to be current, but that also means you must buy a new one yearly. It is too bad you cannot order the protective plastic cover with it via Amazon.