Williamson was the author of several books on Reformed theology, including study guides for the Westminster Confession of Faith, The Westminster Shorter Catechism, and the Heidelberg Catechism as well as studies in Apologetics (Understanding the Times)  and Eschatology (A Study of Biblical Eschatology).
Williamson authored several books on Reformed theology, including study guides for the Westminster Confession of Faith, The Westminster Shorter Catechism, and the Heidelberg Catechism as well as studies in Apologetics (Understanding the Times)  and Eschatology (A Study of Biblical Eschatology).