Westminster Theological Seminary Bookstore has The Gospel According to the Old Testament Series on sale until December 15. If you purchase three or more individual volumes and automatically get them at 50% off and as always, there is $1 Shipping on orders over $35.
I have not used this series, but it sounds interesting. Here is the publisher's description.
A series of studies on the lives of Old Testament characters, written for laypeople and pastors, and designed to encourage Christ-centered reading, teaching, and preaching of the Old Testament.
The series is edited by Tremper Longman III.