Readers on Amazon consider it readable at 3 - 7 Grade Level.
A popular method used by schools to measure a student reader’s ability is Lexile level or a Lexile Measure. The Lexile Level of Hardy Boys 13: The Mark on the Door is 680L .
Readers of age 8 - 12 years will enjoy Hardy Boys 13: The Mark on the Door .
In their motorboat the Sleuth Frank and Joe Hardy search Barmet Bay for a dangerous stranger who has stolen a valuable boat. Suddenly, in the eerie fog, they spot the craft drifting aimlessly out to sea. What happens next starts the young detectives and their pal Chet Morton on an intriguing adventure that takes them to Mexico and into the comparatively unexplored desert and mountain regions of Baja California. Read more