The 22 Murders Of Madison May

From the critically acclaimed author of Jennifer Government and Lexicon comes mind-bending speculative psychological suspense about a serial killer pursuing his victim across time and space, and the woman who is determined to stop him, even if it upends her own reality.
"I love you. In every world."
Young real estate agent Madison May is shocked when a client at an open house says these words to her. The man, a stranger, seems to know far too much about her, and professes his love - shortly before he murders her.
Felicity Staples hates reporting on murders. As a journalist for a mid-size New York City paper, she knows she must take on the assignment to research Madison May's shocking murder, but the crime seems random and the suspect is in the wind. That is, until Felicity spots the killer on the subway, right before he vanishes.
Soon, Felicity senses her entire universe has shifted. No one remembers Madison May, or Felicity's encounter with the mysterious man. And her cat is missing. Felicity realizes that in her pursuit of Madison's killer, she followed him into a different dimension - one where everything about her existence is slightly altered. At first, she is determined to return to the reality she knows, but when Madison May - in this world, a struggling actress - is murdered again, Felicity decides she must find the killer - and learns that she is not the only one hunting him.
Traveling through different realities, Felicity uncovers the opportunity - and danger - of living more than one life.

Max Barry