On a transcontinental flight yesterday, I finished "The Cipher" by Isabella Maldonado, a former police captain turned crime writer.
It's definitely a page-turner, but also a bit of a turn-your-brain-off book. Basically, "What if Zodiac Killer, but on Facebook?"
That said, many other reviews are more positive than mine; if "suspension of disbelief" is no issue for you when reading a story like this, you may enjoy it:
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