1980/90s scifi book abt librarian who recommends 3 short stories to two students at an alien university

As I remember, this might have been a young adult book. Two alien students at university seek the help of the librarian in finding research material. He recommends three "books" which are short stories within this book.

One story was about a young girl on the edge of adulthood who takes her father's space craft on a joy ride. She encounters a derelict ship with two men who died horribly from contact with an alien lifeform that drove them insane. She manages to communicate with this life form and realizes that safe contact is impossible. She drives her ship into a sun to save humanity from this organism.

A second story is about two families in a space empire that have been connected for centuries. A family on a small, backward planet serves the Emperor's family in a very special capacity. The Emperor's heir is always sent to this planet to be "judged" for his fitness to rule. The current Emperor's son proves to be a coward when he compromises the honor of peasant girl and then denies his obligation. He dies (is killed?) and the Emperor is informed that his son was judged a coward and unfit to rule.

I don't remember the third story.

I lent the book to a young neighbor and never got it back. Now I want to read it again.