Things Hoped For by Andrew Clements (2006)

The second of a three-book series that continues Bobby’s adventures. He helps Gwen, an aspiring violinist, solve the mysterious disappearance of her grandfather; in the process, they must deal with another invisible person.

Things That Are by Andrew Clements (2008)

The third of the three-book series, this one features Alicia. Now 17, she works with Bobby to resolve the problems that arose in the second book with the other invisible person.

The Invisible Man by H. G. Wells (1897)

This early sci-fi work tells of a power-mad scientist who figures out how to make himself invisible but can’t reverse it and becomes violently deranged. The book gets a big mention in Chapter 17 of Things Not Seen.

• The Invisible Man on SuperSummary

Invisible Man by Ralph Ellison (1952)

This novel about prejudice against African Americans describes the adventures of a young man who feels invisible in white-American society. His attempts to rally others to resist such treatment are frustrated by the self-serving ambitions of various community leaders. The book won the National Book Award and is featured on multiple 100-best-books lists. This book explores the concept of going unseen despite being visible, a theme explored in Things Not Seen.