The Outlaw Demon Wails by Kim Harrison (Hardback) Eos An Imprint of Harper Collins, 2008.
To save the lives of her friends, Rachel did the unthinkable: she willingly trafficked in forbidden demon magic. And now her sins are coming home to haunt her.
As Rachel searches for the truth behind a terrifying murder, an even greater menace threatens, for the demon Algaliarept will stop at nothing to claim her, and the discovery of a shocking family secret throws Rachel's entire life into question. If she is ever to live free, Rachel must first walk willingly into the demonic ever-after in search of long-lost ancient knowledge.
But when you dance with demons, you lay your soul on the line...and there are some lines that should never be crossed.