Spells of blood and kin

the long version

"When her beloved grandmother dies suddenly, 22-year-old Lissa Nevsky is left with no choice but to take over her grandmother's magical position in their small folk community. That includes honoring a debt owed to the dangerous stranger who appears at Lissa's door. Maksim Volkov needs magic to keep his brutal nature leashed, but he's already lost control once: his blood-borne lust for violence infects Nick Kaisaris, a charming slacker out celebrating the end of finals. Now Nick is somewhere else in Toronto, going slowly mad, and Maksim must find him before he hurts more people."--