Introduction:

what is this?

This is a philosophy book in most general sense of the word:
what can we say when asked about our most comprehensive understanding of the world?

Why is it so small? I was expecting a tome?
It's limited size reflects the limited contribution that philosophy can make in our understanding of the universe.
And how much can you say about things we can never know
Much of philosophy would be correcting other philosophies.

Must there be one? Would that be like the best work of art, or the best dish, or the most handsome person in the world, or the most beautiful spot on earth?

What is the true philosophy book?
The true philosophy book should be simple to grasp, initially plausible, and grow in power as you wander the intellectual universe. The true philosophy book should have thoughts to grow on and into

But obviously one can walk the universe in different philosophies
including not this one.
What follows from this being true is not nothing.