This has come up in conversation for me a couple of times in the last week, so I thought I'd pop it in here. The part of writing that you can learn from a textbook is called craft. Perhaps it should be called The Craft in the same way that black magic is often called The Art.
Craft is to writing what theory and technique is to music. Craft means not only how to put words together so they work, but also things like scene structure, story structure, character development, how to handle point of view, techniques like mirroring and so forth. With good craft alone it's possible to write an acceptable story that flows smoothly and that anyone will read. A story that works.
Craft isn't everything. That story might be ultimately unsatisfying if you haven't covered off the other two essential elements: voice and storytelling. Nevertheless, I find it odd that more people who want to write don't invest heavily in learning this stuff, because anyone can do it.
If you're the sort of person who learns well from books, then there are piles of texts about writing craft. I'm dubious about most of them. The only ones that I'd recommend, and this is very much a personal opinion, is the series Elements of Fiction Writing. I like it because each book in the series is written by someone with real practical experience. Also because I agree with most of what they say! Here they are:
Plot, by Ansen Dibell
Description, by Monica Wood
Conflict, Action & Suspense, by William Noble
Beginnings, Middles & Ends, by Nancy Kress. (Great book for teaching basic structure. That's Nancy Kress the SF author.)
Characters & Viewpoint, by Orson Scott Card. (A very great writer. He knows his stuff.)
Scene & Structure, by Jack Bickham. (The best book of the lot, in my unhumble opinion, and very advanced. My favourite "how to write" book.)
But having said that, I strongly believe anyone can learn craft by reading good books and thinking about how they worked. Most writers do just that. I did that. It's like musicians who learned their craft by listening to great songs and picking them apart to see how they were put together.
I'd suggest taking your favourite books, then go through each one, mark out the scene boundaries, and ask yourself what each scene does, why it's there, which characters are in it, how each scene leads to the next, and so forth. A lot of this is very technical and analytical. If you do it enough, you'll discover standard patterns in any given genre. Everyone knows, for example, that there are common techniques across every murder mystery, but few can explain them. Writers learn the techniques well enough to actually use them.