Several (eleven, by my count) mostly early Stephanie Plum titles are on sale for $2.99 each at Kindle and Kobo US. I’m not up for typing out all the titles, but the numbers are Four, Five, Six, Seven, Eight, Ten, Eleven, Thirteen, Sixteen, and Twenty-Two. Visions of Sugar Plums is also $2.99 right now. The links below lead to all of the titles, but also include a few strays.
buy at Amazon US (link for all): http://www.amazon.com/gp/search/?search-alias=digital-text&field-author=janet+evanovich&price=299-299&sort=price-asc-rank