This book is part of the "What Was?" series, and is recommended for readers in the age range of 8 to 12 years old also described as grade levels 3 to 7. This book "What Was the Hindenburg?" by Janet B. Pascal, illustrated by David Groff, covers the history of the Hindenburg, a German airship that burst into flames while attempting to land in New Jersey on May 6, 1937. The exact cause of the disaster is still a mystery.