What sets the Leningrad Codex apart from every other early Hebrew Bible is not its beauty, though its sixteen carpet pages of interlaced geometry are among the best surviving Hebrew book decoration. It is that the manuscript tells you about itself. The colophon names the scribe, Samuel ben Jacob. It gives the year, which converts to 1008 or 1009. And it states what he copied from: manuscripts that had been corrected by Aaron ben Moses ben Asher, the last of the Tiberian masoretes and the authority on the vowel points, accents and marginal notes that fix how the Hebrew text is read aloud.
That last statement is what a textual scholar actually needs. A manuscript with no colophon has to be placed by its handwriting and argued about. This one places itself, and it places itself in the line everyone agrees is authoritative, at one remove. It is not a ben Asher manuscript. It is a careful copy of one, and it says so.
The practical consequence is that when the Aleppo Codex, the ben Asher manuscript itself, turned out to be missing two fifths of its leaves, the Leningrad Codex was the only complete alternative of comparable standing. It became the base text of the Biblia Hebraica Stuttgartensia and of the critical editions that followed, which means that a scholar reading a printed Hebrew Bible today is, in almost every case, reading this book.