Books come from chitanka.info. Tap a book to read it: if it is already in your library it just opens, otherwise it downloads first and then opens by itself. On desktop the tap opens the book’s download in a new tab (solve chitanka’s one-time check if it asks), then you pick the saved .epub; in the mreader Android app it’s built in — if chitanka asks for its check, solve it in the panel that pops up and the download carries on by itself. Length is estimated from size; Smart score is a Bayesian rating so a lone 6.0 doesn’t outrank a well-voted 5.6.