A compelling SF worldbuilding cannot be done without delivering some backstory at the novel’s beginning. This must be done as early as possible without giving away too much and trying not to bore the readers. 

According to On Writing and Worldbuilding, Volume I, by Timothy Hickson:

“[In] Harry Potter and the Philosopher’s Stone […] J.K. Rowling introduces every major concept and virtually every major character in the story with well-hidden expository writing.”

With all due respect for J.K. Rowling and the Harry Potter series, I don’t agree that ‘expository writing’ must necessarily be hidden.

I can quote a few great SF classics where a nice chunk of information is in plain view right in the first page’s heading. It may take the form of a journal excerpt, a quotation from an encyclopedia, or even an interview with one of the secondary characters.

Here are a few examples: 

(1) Foundation, Isaac Asimov:

“HARI SELDON— … born in the 11,988th year of the Galactic Era; died 12,069. […] Born to middle-class parents on Helicon, Arcturus sector […].” From the ENCYCLOPEDIA GALACTICA.

And a few lines below, just after the incipit:

“[…] There were nearly twenty-five million inhabited planets on the Galaxy then, and not one but owed allegiance to the Empire whose seat was on Trantor.”

From these few words, the reader can already learn a lot about the tone and setting of the story:

— It’ll be about a Galactic Empire. The plot will unfold in a nation-state encompassing most of the Galaxy’s habitable planets.

In technical jargon, a Galactic Empire is what astronomers call a Kardashev Type III civilization, which is “a civilization in possession of energy on the scale of its galaxy” (M.M. Cirkovic, 2015);

— It’ll be about a long-lasting human civilization. Isaac Asimov’s future human society survived the so-called Great Filter. As explained in the book Exoplanets by Michael Summers and James Trefil:

“[…] there really doesn’t seem to be anything at all special about the way that life developed on Earth, and given the abundance of planets out there, there is no reason that complex life shouldn’t be quite common. On the other hand, from what we know about the process of evolution, we can expect the winners of the evolutionary game on other planets to be no more benevolent than Homo Sapiens. In this case, the [coming] Great Filter is easy to see. Once an aggressive, warlike species discovers science, they are likely to turn their discoveries against one another and, in essence, wipe themselves out. […]”

— It’ll involve interstellar and faster-than-light (FTL) travel. Isaac Asimov’s Foundation is loosely based on Gibbon‘s History of the Decline and Fall of the Roman Empire. In his monumental work, the XVII century English historian stressed Roman roads’ importance in ensuring efficient communications between the central authority and the dozens of provinces of an enormous Empire. The Galactic analog of Roman roads is, of course, hyperspace. Asimov was one of the first SF authors to use this plot device to sidestep the long time required for interstellar journeys.

Find out more about relaying the backstory in a novel in this post and this post.