Storybundle has 25 writing craft books available for $30 in honour of NaNo this year. These come in downloadable ebook formats, in two tiers. Pay the full or more price, and you get all 25. If you're like me and already have the second tier – available last year – just pay a little less to get the 2015 tier of books.
Get them here – https://storybundle.com/nano