Not the very first lines, but Terry Pratchetts “The Colour of Magic” intro is a lore about the world and universe, and ends with this absolute gem:

There was, for example, the theory that A’Tuin had come from nowhere and would continue at a uniform crawl, or steady gait, into nowhere, for all time. This theory was popular among academics. An alternative, favoured by those of a religious persuasion, was that A’Tuin was crawling from the Birthplace to the Time of Mating, as were all the stars in the sky which were, obviously, also carried by giant turtles. When they arrived they would briefly and passionately mate, for the first and only time, and from that fiery union new turtles would be born to carry a new pattern of worlds. This was known as the Big Bang hypothesis