House of Stolen Time

It's Blake Crouch's Recursion meets Stephen King's The Mist in a claustrophobic sci-fi horror novel where a failed time experiment traps scientists inside a mansion with monsters from outside time. When a reclusive relative dies, Barbara becomes the sole heir to a decaying mansion buried deep in the woods. There is only one condition: she must take possession of the property within four days, or lose everything to a man she has never heard of.
It should be a strange but simple errand: a road trip with her boyfriend and best friend, a few signatures, and a quick return to college life. But Blake Manor isn't just a house. In Blake Manor, the past has not passed. Twenty years ago, Dr. Ray Bradley built a machine beneath its floors that could pause time. The experiment worked... and it kept working. Trapped inside Blake Manor as an endless night descends, Ray and his team of scientists are forced to survive the things living in the dark. Now, somewhere inside the mansion, the machine is still holding time open. The final instructions Barbara receives leave her with an impossible choice: keep the machine alive, or shut it down and face whatever has been waiting for the world to catch up.