Queen's Quest — Suz deMello

Janus is a planet that lacks both tilt and spin. Its Shadowlands is the pewter band of dusk dividing the violently hot Lightside of the planet from its Darkside, which is imprisoned by eternal night. Birth rates on the planet are low and indiscriminate mating and ménage sex are encouraged.

Audryn, Queen of Shadow, has reached that time in her life when she must choose a king to rule with her or fail to bear an heir, casting not only her realm but all of Janus into chaos. Despite her duty, she is reluctant to share power, even a bit distrustful. Janus' nobles vie for Audryn's hand. Although she enjoys trysting with all her suitors, none seize her heart.

Then Storne, the warrior Prince of Darkness, arrives to claim her as his bride, and she finds she cannot resist his masterful ways.

Inside Scoop: This book contains lots of hot ménage action including an F/F/M scene.