Haunted library (Dori Hillestad Butler)

"When ghost boy Kaz's haunt is torn down and he is separated from his ghost family, he meets a real girl named Claire, who lives above the town library with her parents and her grandmother. Claire has a special ability to see ghosts when other humans cannot and she and Kaz quickly form a friendship."--Amazon website.

Investigating a classmate's claim that he saw a ghost backstage while rehearsing for the school play, Kaz and Claire, harboring suspicions that the ghost may be Kaz's mom, discover compelling evidence of otherworldly activities.

Now that Kaz can finally pass through walls without feeling all "skizzy," he can go explore Beckett's secret room at the back of the library. What he finds there is a mystery he never expected!

The wind separates Kaz the ghost from his family and carries him to a library far away. When he meets Claire - a human who can actually see him - they must work together and solve some mysteries to find Kaz's family.

When a series of strange ghostly happenings disrupts Seattle Public Library's Halloween party, it's up to Kaz, Claire, and Little John to go underneath the city and investigate.