Directly using "Contraption":
* The Curious Contraption of Dr. Z
* The Clockwork Contraption
* A Contraption for the Ages
* The Contraption That Changed Everything
* The Secret of the Contraption
Using related words:
* The Gadget
* The Gizmo
* The Invention
* The Machine
* The Mechanism
* The Apparatus
* The Devise
You can use these examples as inspiration to create your own title that fits the theme of your book. Remember, the best title will be unique and capture the essence of your story.
Consider the genre and target audience of your book. For a children's book, a more whimsical title might be appropriate. For a science fiction novel, a more technical title might be better.