A lot of people complain about the notes in the New American Bible, but I find that they can be helpful in correcting the translation itself. For example, in Mt 12:39, Jesus replies to a request from some scribes and Pharisees for a sign with:
"An evil and unfaithful generation seeks a sign, but no sign will be given it except the sign of Jonah the prophet."
A note points out that the word translated as "unfaithful" literally means "adulterous."
I'm sure the translators had their reasons to use "unfaithful" rather than "adulterous." It sounds more religiousy, and implies a broader spectrum of sins against God.
But it also loses the sense of intimacy, of exclusivity, implied by the language of a marriage bond between God and Israel.
By itself, "unfaithful" is a relatively weak negative. You can be unfaithful to a sports team, or to your home town. With respect to God, if you still believe in Him and don't literally offer incense to some pagan god, would you really say you've been "unfaithful"?
But "adulterous" is not a weak word. It's hard to dance around. And it makes you wonder what it could mean to commit adultery against God. Then, when you find out, when you realize the First Commandment doesn't just mean no pinches of incense to some pagan gods, but putting anything or anyone before God at any moment, when you realize that God wasn't joking when He said He was a jealous God... then you start to understand what it means to be faithful, that it's not just consent to a set of propositions but a commitment to live in a loving relationship with our Creator and Father.
Then you begin to see how ugly it is to insist on a sign from Him.