Stephanie Plum Between the Numbers/Holiday Novels

Four holiday and in-between stories that slot into Janet Evanovich's Stephanie Plum series: Visions of Sugar Plums, Plum Lovin', Plum Lucky and Plum Spooky. Stephanie, the Trenton bounty hunter, is paired with the mysterious Diesel, whose odd talents lead her into holiday-season trouble. Each can be read without the numbered books, though they fall between them in the main series' timeline.