Chasing Nightmares - Dreamscapers, #1

Twenty-one-year-old Ash O'Shea has always been aware in her vivid dreams, and if she concentrates she can control them. She never thought much of it, not until she started ending up in other people's dreams. Usually, their nightmares. She can't stop herself from stumbling in and doesn't care to find out what happens if she dies in one. Then Ash meets others who call themselves dreamwalkers, including an annoyingly cryptic man who shows up in her own dreams with a warning.
He tells her about a prison crafted to hold the most powerful dreamwalker to have ever lived. and that prison is weakening. Unfortunately, the location of the prison is a deeply buried secret, one that only a handful of people know. In the race to stop the return of a vengeful murderer, Ash must learn to navigate the endless possibilities of the dreamscapes, where the only limits are those imposed by her own imagination.