Originally posted by Wolseley
It's complete in and of itself, but it was never meant to be all-inclusive. The Gospels are broad summaries of Jesus' life and mission, written to people who already knew the Faith (as Luke explains in the prelude to his Gospel), and the Epistles are explanations on points of doctrine and practice, also written to people who already knew the Faith. Paul tells his converts to pay attention to both letters AND to word of mouth, if it's coming from an Apostle (2 Thess 2:15); and John says that not everything that Jesus ever did was written down (John 22:25); Acts 8:31, 2 Peter 1:20, and 2 Peter 3:16 make it clear that "Scripture alone" isn't enough---somebody outside it still needs to explain it. We believe that's what Tradition does.
The Bible was never intended to be a "Handbook of Christianity" with the answers to every question. Your mileage, of course, will undoubtably vary.
