Answer:
The Eagle Nebula is probably the best choice as a book of fact.
Explanation:
I think there are actually two answers to this, but one is more certain than the other.
The Eagle Nebula is probably about a Nebula that does not enjoy a good round hoops when it has nothing else to do. Since it is an actual Nebula that is 7000 light years from Earth, any book about it is going to be very factual (and perhaps a bit dry for most people.)
You can't disregard Deep Blue. That too would be pretty factual, but there would be human parts to it as well.