It was once said that "To be truly memorable a story must have at its core one of life's great quests: the quest for love, truth, or power." Essentially meaning that what makes a story interesting, and have an unforgettable plot and theme is for the objective of its main characters or any character to work toward the goal of finding or protecting love, truth, or to obtain power. I agree with this. My position on this will be illustrated with two books I have read, Oedipus and The Princess Bride.
In Oedipus the main goal for Oedipus is the quest for truth. In attempt to find out who King Leais" murderer is, clues are revealed which adds to the plot formation and keeps the reader interested and entertained. Interestingly enough, this is what leads to the downfall of our main character. This quest for truth is what makes the book memorable.
Another such minor quest displayed was for truth as well. When Oedipus lived in Corinth and a prince there, he was once told by a drunkard that he wasn't his fathers son. As a result the ever curious Oedipus wanted to obtain the meaning behind the statement. His quest leads him to prophet who tells him he will kill his father and marry his mother. Fleeing Corinth, and not realizing he was adopted adds to the plot and builds it to events that destroy Oedipus in the end. .
In the Princess Bride the concept of power was portrayed by Prince Humperdinck. He wanted more than anything to rule, so he could start a war. He was even willing to marry someone beautiful without even loving them. And even though the Princess refuses and tries to escape him he is persistent in capturing her and forcing her to marriage for the benefit of power. This fight for power is what the plot is mostly involved with at the end of the book, leaving the last impression, and making this fight for power a memorable factor in the legacy of The Princess Bride.
A second more relevant and overall quest was the quest of love.