Instruct: Classify a given review into positive or negative sentiment.
Query: Definite keeper for future reference!

Although we used the 8th ed in a recent course, it is probably the most well thought out O.R. intro you will find - good relevant case study material for the interested practitioner as well. Not too mathematically rigorous w.r.t. research, but examples are detailed enough, and the book also has a great selection of seemingly real-life practice problems. I especially appreciate ancillary chapters (e.g. crystal ball, project mgmt) being kept on the CD-ROM, it makes it a lot easier to carry and read on the train!