If your thesis is specific enough, it will make a point that focuses on only a small part of the text you are analyzing. You can and should ultimately apply that point to the work as a whole, but a thesis will call attention to specific parts of it. Let's look at those examples again. (This is the last time, I promise.)

A: By telling the story of Westley and Buttercup's triumph over evil, The Princess Bride affirms the power of true love.

B: Although the main plot of The Princess Bride rests on the natural power of true love, an examination of the way that fighting sticks--baseball bats, tree branches, and swords--link the frame story to the romance plot suggests that the grandson is being trained in true love, that love is not natural but socialized.

One way of spotting the problem with example A is to note that a simple plot summary would support its point. That is not true of example B, which tells the reader exactly what moments the paper will discuss and why.

If you find that your paper leads you to mark relevant passages on virtually every page of a long work, you need to find a thesis that helps you focus on a smaller portion of the text. As the MTS reminds us, the paper should still strive to show the reader something new about the text as a whole, but a specific area of concentration will help, not hinder, that effort.