As you know eclipse occurs between two objects when a third object comes between them and subsequently obstructs your view. Normally, we experience two types of eclipses on earth: one is lunar and another is solar eclipse.
In part 26, Bella and Jacob meet for the last time, though Jacob knows that he has lost the fight, yet, he pleads with Bella that he would be better choice and better boyfriend for her as he is like a sun not a drug like Edward for her. She acknowledges his thought of him as a sun that could balance clouds in her life, and Jacob replies, “The clouds I can handle. But I can’t fight an eclipse.”
Thus, ostensibly we are experiencing a solar eclipse, or simply the title points towards the resolution of story: Edward is being a cold moon eclipses Jacob being a warm sun. But, keep in mind that eclipse never last forever and eventually sun returns breaking through the shadows of moon. This could be a sequel to “Breaking Dawn.”