How the reader is made
Language through Literature is built by Tom Besinger in Vienna. The original literature and the assistance beside it have different sources.
The books
The original works come from public-domain texts. The Russian running text uses modern spelling; historical spellings may appear in titles and decorative elements. The German and Spanish rooms identify their editions on their book pages. Any adapted retelling is labelled separately from the original.
The help beside the original
The dictionary forms, word meanings, stress annotations and sentence translations accompany the original texts. Dictionary checks and feedback from readers and teachers have led to corrections.
The prepared help is stored with the reader and appears when you touch a word. The sentence translations are aids to following the original, not quotations from a named published translator. The narration is a synthetic voice: every line is read aloud by text-to-speech, not by a human reader.
Corrections to particular passages do not amount to expert certification of every line. Word senses, grammar, stress and translations can still be wrong. If something looks wrong, please send the book title, the sentence and your correction to Tom.
What the measurements mean
Vocabulary coverage counts how much of a text falls within a particular word list. A sentence with all its dictionary words covered can still be difficult: syntax, idiom and context matter too. These counts are not comprehension tests, CEFR certification or proof of learning gains.
The reader is designed to make consulting help easier while you read. Whether it helps you understand and remember a particular passage is something to try and assess; no rate of progress or fluency deadline is guaranteed.