No, that fish tank isn't spilling off the book shelf, that's just the way the clever blown glass design looks. Because the Bubble Tank, by Psalt Design, is designed to look like it is dripping off the surface where it is set, it only takes up about half the space that it looks like it should.
Even if you don't really think fish bowls are good for fish, it still can be a cool home accessory to use as a terrarium or even just a storage bowl.
Check out more great pictures of the clever fish tank over at Homes and Hues: A More Fluid-Looking Fish Bowl