Obviously, everything in fiction is made up; it is fiction after all. I enjoy speculative fiction, in particular, and it always has made-up stuff in it. For example, we cannot travel at faster than the speed of light. This is not a technical barrier; this is a law of nature. It is impossible to travel faster than the speed of light. So, when a novel has this: it's totally fine. Readers suspend their disbelief.
However, I strongly believe there are only so many disbelief-suspensions allowed in a novel. When authors write about facts, they need to get them right. For example, if an author says the War of 1812 was fought between the U.S.A. and Mexico, I say, "No." (If the novel is an alternate history, this could work.) If an author writes humans have 12 pairs of chromosomes, I say, "No." (Unless it's some kind of super-duper weird mutation.) You get the idea.
Some people call this external consistency. The fictional world should be consistent with reality--unless noted (see speed of light, above). There are other kinds of consistency in fiction: genre consistency. The fictional world should behave like other works in its genre--unless noted. Any fictional characters, settings, concepts, etc. borrowed from other works need to behave as they do in those works. And there's also internal consistency. Any fictional world should be consistent with itself. Characters, settings, concepts, etc. established in a fictional world need to continue to function and exist as they did previously--unless noted. IMHO, writers need to utilize all three kinds of consistency.
What do you think?