In the Care of Magic by Robin Jo Margaret

Jillian Docherty is the only witch in a town of humans, who regularly take advantage of her magic services. Overworked and underappreciated, she escapes her town for a much-needed holiday in her childhood home: a lovely cottage situated deep into the woods.
When she comes across a very unexpected and interesting book promising her company and pleasure, Jillian realizes she may have finally found the relaxation she desperately craved. But she never expected to make friends with a sex demon…