I read part of this book 25? years ago. It was a stand alone book or maybe the first in a series. The book was “normal” sized, not hugely big.
I only read a half to 2/3rd of this Sci-Fi book, do not remember even how it ends.
The female protagonist ( late 20’s, early 30’s ) is coming back home after years away. Maybe hilly, maybe country like area. But the family lives in a large large home that has mirrors on many surfaces. Somehow they help Earth by using the mirrors. Going thru the mirrors?
Her family helps Earth along with some other families that have mirrors.
There’s an attractive Sheriff new to town who sparks her interest. He has friends from his military days who send him beers. He was special forces and likes the different beers his old buddies send him.
He tells her that he knows there is something going on with the family / maybe the small town? / but he trusts the folks and hopes they would tell him what was going on.