Pirates Past Noon By Mary Pope Osborne

Jack and Annie are ready for their next fantasy adventure in the bestselling middle-grade series—the Magic Tree House!

It's a treasure trove of trouble!

Jack and Annie are in for a high-seas adventure when the Magic Tree House whisks them back to the days of deserted islands, secret maps—and ruthless pirates! Will they discover a buried treasure? Or will they be forced to walk the plank?
 
- Goodreads Summary