Coincidence!
The Sentinel by Jeffrey Konvitz is on sale for $1.99 at Amazon US. I read the book years ago and enjoyed it.
Quote:
Aspiring model Allison Parker finally moves into her dream apartment: a brownstone on Manhattan’s Upper West Side. But her perfect home quickly turns hellish.
The building is filled with a cast of sinister tenants, including a reclusive blind priest, who seems to watch her day and night through an upstairs window. Eventually, Allison starts hearing strange noises from the empty apartment above hers. Before long, she uncovers the building’s secret and is plunged into a nightmare of sinful misdeeds and boundless evil.
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There's a sequel, The Guardian which I didn't like nearly as much.
The Sentinel was filmed fairly faithfully. I enjoyed that as well.