So Wrong So Right by Erica Marselas

Abigail knew it was wrong to fantasize about her step-brother, but she couldn’t help herself. Colin had been the only good in her life after their parents married.
After a year of trying to worm her way into his heart, Abigail had convinced herself she’d never be able to have him. Then everything changed one night when Colin kissed her and confessed his own desires.
There was just one problem…
Victor Wagner.
A man with a heavy fist and lingering eyes and who Abigail considered to be Satan disguised as her stepfather.
Despite their fear of Victor’s wrath, they give into their temptation because it feels oh-so right. But if he ever discovers the truth about their relationship, there will be hell to pay.