"In My Place Condemned He Stood" (J. I. Packer and Mark Dever) - This is a collection of essays concerning substitutionary atonement, the doctrine that Jesus' death on the cross was in place of the just punishment we deserved - and His death satisfied God's wrath at our sin, permitting us to enjoy eternal life with God.
The essays are:
The Heart of the Gospel - J.I. Packer (1973)
What Did the Cross Achieve? The Logic of Penal Substitution - J.I. Packer (1973)
Nothing But the Blood - Mark Dever (2006)
Saved By His Own Precious Blood: An Introduction to John Owen's The Death of Death in the Death of Christ - J.I. Packer (1959)
The last section is an overview and recommendation of the work of John Owen, who apparently wrote a lot of excellent material on this subject.
After becoming a Christian, substitutionary atonement has never been a problem for me. But it is a topic always worthy of study. These articles are excellent, both as polemic against alternative proposals, and apologetics for the orthodox doctrine.