Changing Tides by Catherine Hapka appears to be aimed at middle school / young adult readers , roughly ages 12–17. It’s also described as a juvenile fiction title in the National Treasure line.

Quick Scoop

  • Best reading age: about 12–17.
  • Format/genre: juvenile fiction / adventure, tied to the National Treasure universe.
  • Why that range fits: the book is marketed as a middle-school-friendly companion series rather than an adult novel.

Extra note

Different stores and databases can label the same book a little differently, but the clearest age guidance I found points to young adult / middle school readers.