I am writing a book about what our world would be like if there were four spatial dimensions instead of three. While I have done my best to make it entertaining, it is at base a work of 4D geometry. Like, how to make a tennis racquet if you lived in a 4D universe. This is a very limited market. It doesn't fit into any genre.

There is no math in the book -- a sure sales-killer -- but I want to make it clear that this isn't a fantasy. At least, no more a fantasy than is mathematics and geometry in general. Others can check the work and see whether it is correct or not.

What should the title be? A good title should attract those who would like the book and repel those who would not. There are two basic problems.

The first problem is that when I say "four dimensions" people always say, "doesn't it have four dimensions already?" They mean three of space and one of time. I'm talking about four of space and one of time. How to avoid this confusion in a single sentence? I don't know. I can use 4D, 5D, or hyperdimensional. This leads to the second problem.

Searches for "5D" or "Hyperdimensional" turn up nothing but crackpot science and whoo-whoo New Age thinking. It is important that my title repel New Age readers. They would be disappointed. My target market -- if there is one -- is more like high school students who are interested in geometry but bored by what they are being taught. The title should attract them.

Should I use 4D, 5D, hyperdimensional, higher dimensional, "four spatial dimensions" or what?
How do I attract budding engineers and scientists?

That question aside, here are my best efforts and my objections

Everyday Life on a 4D Earth

That's a pretty good title but will be mistaken for fantasy. I think "How To" sounds more nonfiction.

How To Visualize a 4D Earth

An accurate description. It can teach you how to do it. Its too bad that "visualize" has such a strong New Age connotation.

How To Build a 4D Earth

It IS a world-building exercise, as in building an imaginary world. The term "world building" is recognized and might attract the right readers.

How To Engineer a 4D Earth
Accurate. I just hope people don't mistake it for the work of a lunatic who believes it is literally possible.

Imaginary Engineering: How To Build a 4D Earth