•Why it earns a slot
Why it earns a slot: it is the template for every "descent into the unknown" adventure since, built on a real 19th-century scientific debate about what lies beneath the earth's crust, and its ending twist (in through one volcano, out through another) still reads as a clean, earned payoff rather than a contrivance.
A stammering geology professor drags his nephew down an Icelandic volcano chasing a dead alchemist's cipher, and they do not stop until they hit a sea full of living dinosaurs.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.