A Darkness Strange and Lovely (Something Strange and Deadly #2) by Susan Dennard
Publication Date: July 23, 2013
Goodreads Summary:

Following an all-out battle with the walking Dead, the Spirit Hunters have fled Philadelphia, leaving Eleanor alone to cope with the devastating aftermath. But there’s more trouble ahead—the evil necromancer Marcus has returned, and his diabolical advances have Eleanor escaping to Paris to seek the help of Joseph, Jie, and the infuriatingly handsome Daniel once again. When she arrives, however, she finds a whole new darkness lurking in this City of Light. As harrowing events unfold, Eleanor is forced to make a deadly decision that will mean life or death for everyone.
I didn't expect to love the first book as much as I did. And that ending made me eager to read more What books are you waiting on?