The House at the End of the World

 Fiction by Dean Koontz.

https://www.barnesandnoble.com

Katie has lived alone on an island called Jacob's Ladder for two years now, and she has enjoyed the solitude, recovering from the tragic loss of her husband and daughters. Now there has been a disturbance on neighboring Ringrock, an island with some kind of secret government facility, and it looks like the problem over there might be spilling over to Katie's island. 

This was an exciting story with some surprises, although it was a little overblown in places.

I also read recently by this author: Quicksilver