From the reviews:
Julia Day's Fade to Us is a story about found families, the bond of sisterhood, and the agony and awe of first love.
Brooke's summer is going to be EPIC― having fun with her friends and a job that lets her buy a car. Then her new stepfather announces his daughter is moving in. Brooke has always longed for a sibling, so she’s excited about spending more time with her stepsister. But she worries, too. Natalie has Asperger’s--and Brooke's not sure how to be the big sister that Natalie needs.
After Natalie joins a musical theater program, Brooke sacrifices her job to volunteer for the backstage crew. She’s mostly there for Natalie, but Brooke soon discovers how much she enjoys being part of the show. Especially sweet is the chance to work closely with charming and fascinating Micah--the production’s stage manager. If only he wasn't Natalie's mentor...
When her summer comes to an end, will Brooke finally have the family she so desperately wants--and the love she's only dreamed about?