The listing, 2 books by Alyson Noel has ended.
These are the first and second books in the series, and it follows the Immortals series.
Radiance: Riley Bloom left her sister, Ever, in the world of the living and crossed the bridge into the afterlife—a place called Here, where time is always Now. Riley and her dog, Buttercup, have been reunited with her parents and are just settling into a nice, relaxing death when she's summoned before The Council. They let her in on a secret—the afterlife isn't just an eternity of leisure; Riley has to work. She's been assigned a job, Soul Catcher, and a teacher, Bodhi, a curious boy she can't quite figure out.
Riley, Bodhi, and Buttercup return to earth for her first assignment, a Radiant Boy who's been haunting a castle in England for centuries. Many Soul Catchers have tried to get him to cross the bridge and failed. But he's never met Riley...
Shimmer:
Having solved the matter of the Radiant Boy, Riley, Buttercup, and Bodhi are enjoying a well-deserved vacation. When Riley comes across a young ghost named Rebecca, Riley soon learns Rebecca's not at all what she sees. The daughter of a former plantation owner, she is furious about being murdered during a slave revolt in 1733. Mired in her own anger, Rebecca is keeping the ghosts who died along with her trapped in their worst memories. Can Riley help Rebecca without losing herself to her own nightmarish memories?
These are paperbacks, and are in great shape. I got them for my birthday, and I already had them ;)