Affinities novella 3, White Matter, follows four adults from the main series during their teenage years. Summary below may contain spoilers if you haven't read Nerve, novel 2.
Olalla Cosmos believes her derelict family can sink no lower until they move to Hastings Street, a shady trailer park where she encounters three strange boys with oddly-colored hair and eyes, akin to the unnatural purple tint of her own. After realizing these boys possess not only similar abilities to her own but also similar mindsets, the four become an inseparable group—and the perfect target for Olalla’s sister and her posse of jocks.
Between external and internal battles, the group seeks to uncover the science behind their supernatural abilities. Such knowledge demands a price, though, and conflicting ambitions don’t nurture relationships built on common goals.