I think most people won't realize was a book before it was adapted by Disney into a film. Firstly, the illustrations which were done by Garth Williams (he also did Stuart Little and Charlotte's Web) are fantastic. They portray Bernard and Miss Bianca very differently from the movie version because their characters are almost entirely different. In fact, everything apart from there being talking mice who form a secret society that help humans was changed. Bianca is portrayed as a rather vacuous female content with her lot in life but Bernard makes her see herself in a slightly different light. The movie is the exact opposite where Bernard is full of timidity and it is Bianca that draws him out of his shell and shows him what he is truly made of. The film is about the rescue mission of an orphan girl named Penny from a truly horrific woman (who reminds me of Miss Hannigan from the musical Annie) while the book is about the rescue of a Norwegian poet from an impenetrable castle. The essential feeling of the two storylines is the same but if I had to choose between the two I'd probably go for the movie on this one (but you should still check out the beautiful illustrations).