Whether you are relatively new to the idea of ‘keeping kosher’ or already quite knowledgeable of the issues, this book is for you. I recommend this book as a beginning place for understanding how rooted in Scripture kashrut is, and its importance for those at the beginning of their journeys.
A rabbi was walking down the street when he saw Benny, a member of his synagogue, entering a non-kosher restaurant. Puzzled, he went closer to the restaurant and peeked in the window. "Perhaps he's just going in to ask for directions or use the toilet," the rabbi thought. But sure enough, he watched as Benny was escorted to a table. 
Studies independently conducted by the Boston Globe and Consumer Reports found similar, troubling results. Fish sold in stores and restaurants are frequently mis-labeled as a different species. This may be due to a number of factors, such as simple mistaken identity, failures of communication, or fraud either on the part of the retailer or the supplier.