Romance writers Leigh (Lion's Heat) and Burton (Riding on Instinct) contribute elements of their best-known series in a pair of steamy novellas. Leigh's "Nauti Kisses" features the sultry southern setting and characters of her Nauti series. John Calvin Walker, Jr. is an attorney who runs away from his privileged life. When beautiful Sierra Lucas, the object of his passion, is forced back into his life, he knows he'll do anything to protect her. As a character, Sierra is underdeveloped, but Leigh's fans will most likely concentrate on the frequent, detailed bedroom scenes. Burton's "Riding the Edge" is the stronger of the two, featuring bad boy biker and undercover agent Rick Benetti and an intriguing and beautiful graduate student named Ava Vargas. When Rick is assigned to investigate why Ava, the daughter of a powerful Nevada senator, has become involved with his old motorcycle gang, he uncovers more than he could have predicted. The breezy plot sweeps readers up into a world of drugs, crime, and unexpected love. (Aug.)