Jules Verne · 1828
Heavy going at CET-4 level. Not unreadable — just not readable the look-every-word-up way.
Coverage = the share of words in the text you already know. The research gives two lines: 98% before independent fluent reading is realistic, 95% for the instructional level that needs support (Hu & Nation, 2000). Proper nouns are not counted as unknown — recognising that it is a name is enough; this book has 372 of them.
Advanced — read it with glosses. 193,212 words in total; at 150 words a minute for a non-native reader, about 21 h 28 min to finish. Average sentence length 17.7 words. Reaching 95% coverage on this book (the floor for readability) takes roughly 17,000 word families.
The opening of The Mysterious Island, word for word. Tap any word you don't know and its meaning here appears beside it — no sign-up, tap as often as you like.
“Are we rising again?” “No. On the contrary.” “Are we descending?” “Worse than that, captain! we are falling!” “For Heaven’s sake heave out the ballast!” “There! the last sack is empty!” “Does the balloon rise?” “No!” “I hear a noise like the dashing of waves. The sea is below the car! It cannot be more than 500 feet from us!” “Overboard with every weight! ... everything!”
Such were the loud and startling words which resounded through the air, above the vast watery desert of the Pacific, about four o’clock in the evening of the 23rd of March, 1865.
Few can possibly have forgotten the terrible storm from the northeast, in the middle of the equinox of that year. The tempest raged without intermission from the 18th to the 26th of March. Its ravages were terrible in America, Europe, and Asia, covering a distance of eighteen hundred miles, and extending obliquely to the equator from the thirty-fifth north parallel to the fortieth south parallel. Towns were overthrown, forests uprooted, coasts devastated by the mountains of water which were precipitated on them, vessels cast on the shore, which the published accounts numbered by hundreds, whole districts leveled by waterspouts which destroyed everything they passed over, several thousand people crushed on land or drowned at sea; such were the traces of its fury, left by this devastating tempest. It surpassed in disasters those which so frightfully ravaged Havana and Guadalupe, one on the 25th of October, 1810, the other on the 26th of July, 1825.
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Computed by Readii from the public-domain text (updated 2026-10-21), not estimated by hand. The Readii reading level is our own scale, anchored on unknown-word density; it is not the same system as Lexile or AR and does not convert directly. Unknown words are measured against the CET-4 ∪ Gaokao lists, so this is difficulty for a Chinese-speaking learner, not a native-child reading level.