What they don't tell you... – Marriott Bonvoy: Book Hotels Review

I received an email saying I can do an early check in if I download the app. What they fail to tell you is that if your room was booked through a third party (Priceline, trivago, etc.) then you will not be able to do an early check in. You are only eligible for early check in if you booked directly through the Marriott. Even if you are a rewards member, which makes zero sense. So if you booked your room through a third party, save the effort and don't waste your time downloading this app.
Review by Ra1derNation on Marriott Bonvoy: Book Hotels.