The Outlaw Demon Wails - Kim Harrison

Vampire and bounty hunter extraordinaire Rachel Morgan must play a dangerous game in which the the prize is her immortal soul in this riveting new tale in the bestselling Hollows series
To save the lives of her friends, Rachel Morgan, witch and runner, did the unthinkable: she willingly trafficked in forbidden demon magic. Now she's about to pay for that sin . . . .
But there was one person her wits and wiles couldn't save. Searching for the truth behind her love's murder, Rachel treads a dangerous path, filled with deadly menace and shocking suprises— including a powerful demon determined to claim her and a family secret that throws her entire life into question. If she is ever to live free, she must walk willingly into the demonic ever-after in search of long-lost knowledge.
But when a woman dances with demons, she lays her soul on the line . . . and Rachel may never return.