Hebrews by David Allen: $2.99 on US Kindle. UPDATE: Discount also applies on UK Kindle.
A good, although not great commentary from a scholar who argues that Luke wrote Hebrews.
Worth it for $2.99.
"Hebrews: 35 (The New American Commentary)" (David L. Allen)
UPDATE
A scholarly look at the Pastoral Epistles for $3.99 on US Kindle.
"Entrusted with the Gospel: Paul's Theology in the Pastoral Epistles" (B&H Academic)
UPDATE:
The UK Kindle price for both these books has been discounted down to £1.99.
Great to see Amazon coordinating the discount for both US and UK. Hopefully for other Amazon stores as well.