Four 'Stephanie Plum - Between the Numbers' books by Janet Evanovich from St. Martin's Press are $2.99 each
Visions of Sugar Plums
Plum Lovin
Plum Lucky
Plum Spooky
(FYI, to save an extra dollar: get
Between the Plums (collection of the first 3 books at $7.59) +
Plum Spooky instead)