Lock Every Door by Riley Sager

Jules is desperate. After being laid off, she returned home to find her boyfriend in bed with another woman. Taking only the essentials, she set up on her best friend Chloe's couch, an offer Chloe says is good as long as Jules needs it. But Jules feels like a burden and is anxious to be gainfully employed again. Which is why she answers a Craigslist ad for an apartment sitter. 

When the apartment turns out to be in the expensive and exclusive Bartholomew, a building featured in Jules's own favorite book, she's sure the offer is too good to be true. 

All she has to do is stay in the apartment for three months. She can't have visitors and she has to spend every night there. Other than that and being warned about the other tenants' need for privacy, it seems altogether too easy for $12,000 cash! But then a fellow apartment sitter goes missing. The official story is that she left, tired of the job. But Jules isn't buying it. And as she digs deeper into the history of the Bartholomew, Jules becomes certain things aren't right at the lofty building. 

With just three books under his belt, Riley Sager has made a name for himself as a master of suspense. And it's undeniably true that every one of his books is an absolute page turner. But I do have to say that I think Lock Every Door is his best to date.

The book is dedicated to Ira Levin, which, if you're literarily savvy is kind of a spoiler as far as a book about a mysterious apartment is concerned. But not really. All it did was set me up for what's pretty obvious from the start, there's something hinky going on at this apartment building!

Even our heroine knows it. But Sager's made her so desperate and in dire straits that she's willing to overlook the odd rules and the cash under the table because it means a roof over her head and money in the bank. And not wearing out her welcome with her best and only friend. So while you can imagine that reading the first pages is akin to yelling at a character in a horror movie not to go up the stairs, you can also easily sympathize with Jules!

Lock Every Door is twisted and suspenseful fun. I ripped through it as fast as I could, even delving into the audio so I could listen when I couldn't sit down and read. And Sager has some tricks up his sleeve as the story progresses. I'd almost guarantee you won't figure out what's really going on at the Bartholomew before Jules does.