The Bible interprets itself in many places where symbols are used. You do not need another book to understand; other than looking for understanding in the whole counsel of God. However, there are places in the Bible that you will not fully understand unless you know a little about history, culture, and such. For the next few days, I am highlighting other books that have been proven over the years as a great asset in helping to understand some difficult passages.
No source, other than the Bible itself, provides more relevant information on the first century than the work of Flavius Josephus.