Mask (Four Regions #1)

Emily thought magic only existed in the books she read as a child. When a handsome stranger enlists her help to uncover who tried to kill the princess of another world, she learns those books were more than just stories. She discovers the Four Regions - a realm where magical creatures fled to escape human persecution. It is there Emily finds the power, passion, and friendships she had always secretly craved.
The determined demon who guides her.
The irresistible vampire who entices her.
The excitable demoness who supports her.
The quiet elf who understands her.
Now Emily must unmask a murderer while wearing a mask herself, resisting a growing temptation that could ruin her newfound family.