How many locative vs. other prepositions are to be found in selected passages of Conrad and Lawrence? A handy three-page chart in Style in Fiction will tell you: it's 20 to 44 and 34 to 18, respectively. In case you were wondering. You weren't?
Well then, how many co-ordinating subjunctions does Henry James use per hundred words? What is the ratio of dependent to independent clauses in his work? Does he exceed the number of modal auxiliaries used in general English? The answer, if you haven't guessed it, is zzzzzzzzzzzzzzz.
Let's put it this way: if you have ever asked yourself, "What is the number of lexical repetitions in great modernist literature, crossed-referenced by personal pronouns and demonstratives?", then this is the book for you. Alternatively, I suppose, if you have ever found yourself struggling to look dead clever in a room full of bright but sarcastic undergraduate creative writing students, then you might find this is just the club to pound them with.
There is no doubt that Style in Fiction is a work of deep and detailed scholarship. It is not, however, a guide for creative writers, no matter how many times Professor Snooty-pants brings it up. This is a specialist text, and lay readers will find it has all the flair of a radio-repair manual. Just as knowing how a transistor works won't guarantee any good music on Radio 1, so does Style in Fiction have little or nothing to do with how to make fiction good, or great. Or touching. Or sexy. Or any of the things we read for. As analysis, it is exceedingly thorough; as a handbook, it is a recipe for plodding.
If you read this book, well, then: you deserve to know everything there is to say about relative norms, and you'll be able to. If that's not your goal, however, you might want to look elsewhere.