Magic Tree House: #4 Pirates Past Noon by Mary Pope Osborne
From Random House Books for Young Readers:
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?
Did you know that there’s a Magic Tree House book for every kid?