You can download a pdf edition of The One True God by Paul Washer. It is structured very differently than most other theological books. It is more like a workbook for a Bible study than an academic textbook. The author intends to get you into the biblical text and to utilize your mind and your heart in the pursuit of God through the Bible. Paul has served as a missionary and is the director of the HeartCry Missionary Society, which he founded during the time of his mission in Peru.