•Why it earns a slot
The Lost World established the template for the lost-world adventure genre, introduced Professor Challenger as one of fiction's most memorable scientific eccentrics, and remains the definitive popular treatment of the idea that prehistoric life might survive in an isolated corner of the modern earth.
Young Irish reporter Edward Malone, spurred by a woman who will only love a man of heroic deeds, joins the volcanic, combative Professor Challenger on an expedition to a remote South American plateau where prehistoric creatures still live. The four-man party—Malone, Challenger, the skeptic Professor Summerlee, and the sportsman Lord John Roxton—reaches the plateau, becomes stranded there, and must survive dinosaurs, pterodactyls, and a tribe of ape-men before finding a way home. They return to London with a live pterodactyl as proof, are celebrated as heroes, and discover that Roxton secretly collected a fortune in diamonds from a volcanic blue-clay pit on the plateau.
This distillation is written from the freely available original, which is always the better read when you have the time: gutenberg.org.