Tweets are spread out through the week, occurring at different times of the day. The tweets are repeated each week. I do not know how long a tweet campaign will last. Once I decide my schedule is full, I'll start replacing the older campaigns with newer ones, which shouldn't be anytime soon, especially for the early advertisers.
Tweets can be composed in a few different forms (with the author's help): review quotes, novel lines, plot summaries, and general tweets to introduce the book and/or author. A link to either the book on Amazon or to a promo post on this site is appended after the text.