The Skylark of Space by E E "Doc" Smith (1928)
Chemist Richard "Dick" Seaton watches in astonishment as his experiment flies out the window and into infinity. Before you can say "radium" Seaton realises he has discovered the secret of atomic energy and without missing a beat gets his best friend to back him in building a spaceship. However, evil mastermind Richard "Blackie" DuQuesne is also after the secret and does all sorts of dastardly things to get a monopoly on the new power source, including kidnapping Seaton's fiancée in a spaceship of his own.
Skylark is one of the true classics of early science fiction, but "classic:" doesn't always translate into good. This is a novel where to call the characters two-dimensional would be a compliment. As to the plot, Smith sets up his chess pieces, gives you a good 360 degree look at them, and then sets them in motion with zero suspense or even conflict. True, there are villains and fist clenchings and all sorts of melodramatic goings on, but none of it means anything because nothing is ever at stake. When our heroes can effectively forget about the black-hearted Duquesne for the last half of the book, something is seriously wrong. Instead, we get spectacles, set piece battles, and escapes that are about as engaging as watching a string of firecrackers go off. And there are banquets. Every time Smith's plot bogs down he has everyone march off to eat.
Worse, most everything depends on a staggering string of coincidences. Our heroes just happens to come across an airfleet bineg attacked by monsters never before seen in such numbers. The fleet just happens to be that of the emperor of the planet they're visiting, who just happens to have the leader of his enemies captives, who the emperor just happens to give the Earthmen as a slave and who just happens to have a thought teaching device he just happens to have just invented. And so on, and so on.
The only thing that keeps this going is sheer brass with Smith rolling out scientific wonder upon wonder in a parade of power fantasies. Small wonder it was such a sensation in 1928. It hasn't the "what the hell" bravado of Smith's later Lensman series, but it does point the way.