Magic Tree House: Books 5 and 6: Night of the Ninjas, Afternoon on the Amazon
Brand: Audible

In Night of the Ninjas, Jack and Annie meet a real live ninja when the Magic Tree House whisks them back to ancient Japan in search of enchantress Morgan le Fay, who holds the answer to the origins of the Tree House. When they arrive, they find themselves in the cave of a ninja master. Will they learn the secrets of the ninja? Or will the evil samurai warriors get them first?

In Afternoon on the Amazon, Jack and Annie are about to run into vampire bats and killer ants when the Magic Tree House whisks them back in time to a South American Rain Forest in search of the elusive Morgan le Fay. It's not long before they get hopelessly lost on the Amazon River. Will they be able to find their way back to the tree house before they are trampled by stampeding killer ants?