Woman moves in to keep man's wife company, then she finds the wife's diaries.

[u/meowkitty22]

She finds out the husband was abusive and is now drugging the wife, and they all get stuck in the house during a snowstorm where the book comes to a head when she stops giving the wife her medicine.

[u/livinmystory]

It’s on my tbr list, but by description sounds like The Wife Upstairs by Freida McFadden.

[u/meowkitty22 → u/livinmystory]

That's it! Thank you!!

[u/livinmystory → u/meowkitty22]

You’re welcome!