In the introduction, Wilson avers that his intention is not to divert attention away from Calvin, but to offer a "gentle nudge" toward the Reformer's Institutes of the Christian Religion. The questions and answers provided here certainly could act as a sort of catechism for newcomers to Calvinism, but a better plan would be to read them side-by-side with Calvin's text and use them as points to ponder or (in a group setting) discuss.
Wilson divides his text by topic, moving chronologically through The Institutes and posing a few questions (usually one or two) with answers. Where necessary, answers include Scripture references; mostly, however, they're simply interpretations of Calvin's doctrine as outlined point-by-point. Each short section has a title for easy reference, and the following questions relate specifically to its fairly narrow doctrinal compass.
A problem endemic to all such "study guides" is that, invariably, the author infuses his own interpretation into the questions and answers, whether he intends to or not. Even the questions asks will direct readers to a particular view of Calvin's work that Calvin may or may not approve. Such interpretation is unaviodable, but it's probably best to share this book with older readers or those who've been exposed to The Institutes, using the questions to spark dialogue rather than to define Calvin's original work.
Another problem: though The Institutes are very long (more than 1200 pages), A Study Guide to Calvin's Institutes is well over 300 pages, making it a bit of an undertaking in its own right. Still, this has the potential to be a good introduction and study guide for those wanting deeper knowledge of Reformed theology, especially if Wilson's commentary is taken with a degree of skepticism and close comparison with Calvin and (more importantly) Scripture itself.