It is What it Isn't — Robin Buckallew

When Tricia begins to meet herself everywhere she goes, her life begins to go terribly wrong. Suspicious that she might have inherited her mother's illness, Tricia consults a doctor, only to bring the doctor into the world of strange events that now surround her. Duplicates begin to multiply, piling up encounter after encounter with persons she has never met who insist she is someone else...or persons she does know who do not appear to know her. From the bank, to the library, to work, Tricia finds herself already there, creating confusion and threatening to destroy her marriage, her sanity, and even her very life.