The trouble with time travel

"Max and her dog, Boomer, are in trouble. Big trouble. Max has accidentally smashed an heirloom vase: the only treasure her great-great-great-great-great-great-grandma managed to save when her houseboat sank 234 years ago. Max can come clean--or, she can build a time machine! If she travels to the past and smashes the vase then, there will be nothing for her to break in the future. . . . In the time machine--surprisingly easy to construct--Max and Boomer bump around to the past and the future, tangle the string of time, and crash into the ancestral houseboat, promptly sinking it. And in the past, the vase remains intact. Disheartened, Max and Boomer return to the moment just before their adventure began, to warn themselves NOT to build a time machine. In spite of the warning, Max tosses a Frisbee for Boomer, directly in the direction of the vase, and their wild adventure begins again, and again, and again..."--Provided by publisher.