The Sommelier Prep Course: An Introduction to the Wines, Beers, and Spirits of the World

by Michael Gibson, 2010
This is one of the books in my library which I have used to prep for the WSET and CMS Level 1&2.  It is thorough enough for the lower level qualifications, and is a handy quick review for more advanced study.  One of the benefits of this book is that it has review questions on each section which can test your knowledge.  Not really for advanced study, it is most helpful for those looking to make the jump into taking tests.  I recommend this to staff on a frequent basis if they want to dip their toes into more advanced material, as it is an organized approach to the study of wine, beer and spirits, as well as service protocols, and is perfect for service professionals.