I recommend "Paul and Jesus - How the apostle transformed christianity" by James D. Tabor and "Jesus, Interrupted", by Bart Ehrman.
It will establish firmly that what we know as "christianity" today wasn't the message of Jesus, but essentially a Pauline creation. Jesus was a radical apocalyptic prophet / Jewish rabbi with no intention to establish a new religion and with a very specific concern with his time, not the distant future. Which raises the question: If Jesus wasn't what the Bible tells us he was, did and said, why bother with things like the Heavenly Kingdom of God, the Armageddon, The Paradise on Earth, the Original Sin, the Ransom, Resurrection and Eternal Life. It made me re-think my whole take on christianity itself.
Eden