When we think of the Roman Empire, we think Latin. In fact, at the time of Jesus, Greek, not Latin, was the language of the Empire. Just as today we read our Bible in English, Jews of that time would have more often than not used the Greek translation called the Septuagent.
The name Septuagent comes from the Roman numeral LXX (70). It is the number of Jewish scholars who translated the Torah into Greek to make it accessible to the people. People in the time of Jesus did not speak Biblical Hebrew. Even Jesus spoke Aramaic.
St. Paul and the others who wrote the New Testament depended on the Septuagent when quoting the Old Testament. While it is true that later in history Judaism would reject the Septuagent, Catholic and Orthodox Bibles hold on to it because it was the Old Testament of the Early Church.
When we read the Septuagent we are reading not some later, rarified Hebrew Old Testament, but the Old Testament as it would have been read by the first Christian communities. Your Catholic Bible contains all of the books that would have been in the Septuagent. Other bibles have taken out some of the books. I am often perplexed by some Christian theologians who will quote St. Augustine and reject the Bible that he would have read.
Today we begin reading the book of Tobit. If you had asked St. Paul was it really part of the Bible, he would have said of course. It would not be until the 16th century that some Christians would reject it. It is not the case as I heard growing up that "Catholics added to the Bible." We simply remain faithful to the Old Testament that would have belonged to the earliest Christians.
The Book of Tobit is the story of a man who remains faithful to God's law even in exile. He is willing to risk everything to provide his fellows Jews with a proper burial. This week we will read not only how he suffered but how the angel Rafael came in disguise to assist him because of his faithfulness in things large and small.