Funny, I've just started reading Dumas'
The Three Musketeers again a few days ago and it reminded me how close
this cartoon from my childhood was to the original, all things considered. Obviously it was adapted for children and it's a long story in the first place so it's a very hard one to tell in a limited time, but it remains surprisingly close to the original. Some scenes are basically identical, others were completely made up but will still include key elements from the original story. Nice work.
Who would have thought that a kids show, with all the characters portrayed by dogs (!), would still be more faithful to the original than many serious movies?

Oh, and I've just remembered another one: it was an anime adaptation of Louisa May Alcott's
Little Women. The book was written in English, then the Japanese made the series and I watched the French dub. Amazingly, when I finally read the book online a few years ago, the series is incredibly close to the book. I don't know if we could say that it was word for word but it could hardly be closer because I recognized some of the dialogues.