Some of the critical theory books are really interesting. With regards to studies of structure and plot I would recommend . . .
The Seven Basic Plots by C. Booker
The Writer's Journey by C. Vogler
Check out De Saussure's work on linguistics if you get time.
For a writing related book I recommend . . .
Self Editing For Fiction Writer's: How to Edit Yourself Into Print, by Rennie Browne and Dave King
I'm on the lookout for some good grammar books -- if anyone else has some recommendations, throw them my way too, please
Then, as David says, get hold of and read different styles of writing. Try stuff out of your genre, in your genre, different authors. You'll start to see the patterns.