It is arbitrary but that doesn't make it meaningless. "Just use one font" is the "just eat only soylent" of typography. It ignores or dismisses the fact that arbitrary aesthetic factors do affect us and how we approach or receive a text.

Abolition looked totally wrong at first, but the next step increases the size of the title and makes it look more balanced with the rest of the page.

Sci-Fi doesn't need to be all slab-serif and uppercase, but I think the author's suggestion captures the usual clichés about the genre pretty well. It's a decent introduction for typesetting a typical Sci-Fi book. Web pages, not so much.

The font is there to set a mood and context.

It has to be legible, but it also has to signal what readers are going to get.

No one is going to set a science fiction novel in this. It would be too weird.

https://commons.wikimedia.org/wiki/File:Old_English_typeface...

Similarly using different fonts for title, subhead, and body gives readers a preview of the content.

Abolition is good for the title.

Personally I didn't agree with the subhead choice because I thought it was too on-the-nose and cliched.

But it's a fine line, and originality always has to be balanced with expectation.

> No one is going to set a science fiction novel in this. It would be too weird.

Well, Carl Amery's "Der Untergang der Stadt Passau" at least includes passages styled after medeavial chronicles, that are set in Fraktur.

As a university teacher of mine once said: Write down a set of rules for a genre and you get a manual on how to violate it.

> Abolition is good for the title. / Personally I didn't agree with the subhead choice

Well... that confirms my point: it's arbitrary, a matter of opinion, and therefore, everyone is going to have a different preference.