Sticking with tattoo themed books - I can recommend, 'A Good and Useful Hurt' by Aric Davis.
It's a tad gruesome in places, both with the serial killer and the descriptions of the body modifications in the shop... It's an interesting premise and an enjoyable read.
Blurb:
Mike is a tattoo artist running his own shop, and Deb is the piercing artist he hires to round out the motley crew at his studio of four. The last thing either expects is romance, but that’s exactly what happens when they follow their off-kilter careers and love lives into complete disaster.
When Mike follows a growing trend and tattoos the ashes of deceased loved ones into several customers’ tattoos, he has no idea that it will one day provide the solution—and solace—he will sorely need. And when the life of a serial killer tragically collides with the lives of those in the tattoo shop, Mike and Deb will stop at nothing in their quest for revenge, even if it means stepping outside the known boundaries of life and death.
Ink that is full of crematory ashes, a sociopathic killer, and pain in its most raw form combine for one of the most imaginative, haunting thrillers in recent memory. Full of wit and heart, A Good and Useful Hurt delivers the goods with the pain of a needle in skin.