I just got Piper's new book Contending for Our All last night. It is the fourth book in his "The Swans are not Silent" series. This book looks at the lives of Athanasius, John Owen, and J. Gresham Machen and their fight for the truth.
Just a little hint: The introductions to these four biographical books are fantastic! Having read the previous three, I immediately read the introduction last night to this new one. I was once again humbled and broken. In these introductions, Piper merges the lives of the three men he is writing about and describes the dominant theme of their lives as he sees it. These introductions are among Piper's best writing. One day, when he publishes "The Swans are not Silent, book twenty", I hope someone will combine all the introductions into one powerful book.
Piper ends this introduction with a quote from Martin Luther:
"If I profess with the loudest voice and clearest exposition every portion of the truth of God except precisely that little point which the world and the devil are at that moment attacking, I am not confessing Christ, however boldly I may be professing Christ. Where the battle rages there the loyalty of the soldier is proved, and to be steady on all the battlefield besides is mere flight and disgrace if he flinches at that point."