This month's free audio book from ChristianAudio.com is the Christian classic The Holiness of God by R.C. Sproul. Here is the brief summary description from the publisher's product page for the book:

“When people ask me to name the Ligonier teaching material they should use to help them grow; I tell them, ‘You should start with The Holiness of God.’” - R.C. Sproul

Now celebrating 25 years of publication, this classic can help you better understand the biblical picture of God’s awesome holiness and why it is so foundational to God-centered, God-honoring theology and Christian living. In The Holiness of God , R.C. Sproul demonstrates that encountering God’s holy presence is a terrifying experience. Dr. Sproul argues that this struggle is nonetheless necessary because it is the only way to cure our propensity to trust in ourselves and our own righteousness for salvation.

I have yet to meet a Christian who has read this book and who has not been profoundly altered by it. And, since ChristianAudio, Tyndale House Publishers, and Ligonier Ministries have partnered to offer the audio book for free this month, there is no reason not to get it. You may also want to check out other audio books they offer at very good prices.