The Catholic Church considers the Bible to be the inspired word of God:
God is the author of Sacred Scripture. "The divinely revealed realities, which are contained and presented in the text of Sacred Scripture, have been written down under the inspiration of the Holy Spirit."
(Catechism of the Catholic Church, paragraph 105; the quote is taken from the Apostolic Constitution Dei Verbum section 11)
The same paragraph indicates that the Church considers the whole of the Old Testament (listed here; note that Deuteronomy is in the list) as canonical and inspired:
Holy Mother Church, relying on the faith of the apostolic age, accepts as sacred and canonical the books of the Old and the New Testaments, whole and entire, with all their parts, on the grounds that, written under the inspiration of the Holy Spirit, they have God as their author and have been handed on as such to the Church herself.
(Dei Verbum section 11, quoted in Catechism paragraph 105)
These inspired books teach the truths necessary for salvation:
The inspired books teach the truth. "Since therefore all that the inspired authors or sacred writers affirm should be regarded as affirmed by the Holy Spirit, we must acknowledge that the books of Scripture firmly, faithfully, and without error teach that truth which God, for the sake of our salvation, wished to see confided to the Sacred Scriptures."
(Catechism paragraph 107; again the quote is Dei Verbum section 11)
The quote you take from Deuteronomy is thus considered inspired and part of canonical Scripture by the Catholic Church. It doesn't necessarily follow that it is giving us instructions which we ought to follow to the letter, but it does follow that there are truths in the book which are needful to salvation.
How, then, should this passage be used? Is it in fact giving us instruction on how to act in our daily lives? Should we be allowing rapists to marry their victims after paying a fine?
Before the reforms implemented by the Second Vatican Council, there were no, or virtually no, readings from the Old Testament prescribed for Sunday Mass—there was one from the epistles or Acts, and one from the Gospels. It was only afterwards that we began reading regularly from the Old Testament, and it was because Catholics need to look at the Old Testament not on its own, but in light of what it can tell us about the New:
...when the Church reads the Old Testament, she searches there for what the Spirit, "who has spoken through the prophets," wants to tell us about Christ.
(Catechism paragraph 702)
We revere the Old Testament because we can find there a wealth of information about God, about Christ—not because we're looking for laws which we must follow. (Certainly there are laws we must follow; the Ten Commandments for example, which follow from the "two greatest commandments" Jesus pointed out. But not all the Old Testament is like that.)
So: what might we be able to get about who and what God is, from these verses, in the light of Christ? There's no official statement from the Church (this is true of most of the Old Testament); but certainly one sees (for example) the importance and the life-long nature of the marriage bond.