I would argue that with the exceptions of Sweeney Todd and Forum, every Sondheim show has a book that is unworthy of the score he created. Weidman's books are very interesting and thought-provoking, but overreach in their ambition, frequently ending up being somewhat muddled and meandering in spots, Lapine's books are disjointed, too "concept" and not enough coherence in the storytelling and character development and overall lack the incisiveness of the music, Furth's vignettes for Company and Merrily are cute but sitcom-ish and one-dimensional, while Goldman's work on Follies is melodramatic, morose and lacks conclusion. The Frogs and Bounce (along with a few other shows) lack the sort of singular vision and "through-line" in the book that you find in his compositional work. Perhaps it's too much to hope that Sondheim would work with book writers whose genius is equal to his (do they exist? Laurents' books for Gypsy and WSS, I suppose, match his brilliance as a lyricist), but it's rarely happened in his career.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney