Every Soul a Star is a young adult novel written from the perspective of three pre-teens about their interwoven experiences surrounding an unusual solar eclipse at Moon Shadow Campground. Ally and her family own and manage a campground, which hosts guests who come to see eclipses and other astronomical events every few months. A solar eclipse is expected that has required considerable planning. Ally is an unusual child who is homeschooled at the campground along with her brother Kenny by her parents. She is fascinated by astronomy and is content with her life in preparation for the eclipse, until she learns that her parents are planning to move into a large city, where her father can get a better job. Her world is now threatened.

In a similar way, Bree, the beauty-obsessed wannabe model, who is only a bit older than Ally is content with her life in the city. She is somewhat alienated from her physicist parents and her nerdy little sister, Melanie. Bree finds out from her parents early in the book that they're going to move to Moon Shadow in order to take the campground over from Ally's family and will use the campground to do their research. Bree is devastated and feels as if her dreams are shattered. The rest of her family is so excited to move that they go on ahead to Moon Shadow before the eclipse.

Jack, a pudgy, artistic boy who has trouble in school has failed science class and must go to summer school until his science teacher and eclipse tour guide, Mr. Silver, makes him a deal. Mr. Silver tells Jack to come with him to Moon Shadow for two weeks and study the eclipse. Then he will not have to go to summer school. Jack begrudgingly agrees.

This is how the three main characters, Ally, Bree, and Jack, cross paths at Moon Shadow prior to the eclipse. Their interactions cause changes in their personalities and understandings of their lives. When Bree and Ally meet, they help make each other more comfortable with their transitions and Jack learns to be more confident through a series of confidence-building events. But what really brings them together is when they all must cooperate to gather data attempting to demonstrate the existence of an exoplanet after Mr. Silver is pulled away due to his wife's health issues. After successfully demonstrating the existence of the planet, "Team Exo" (Jack, Ally, Kenny, Bree, Melanie, and Ally's friend Ryan) celebrate and watch the eclipse together. Afterwards, each of the three main characters reflects on how their experiences changed them for the better. Ally grew friendlier to the world, Bree grew friendlier to her inner geek, and Jack grew more confident and responsible due to their shared experiences.