The answer is: read it. You can follow the anime when you're done, if you like. What is this? But, if you read the manga first, you're treating yourself to the very best version of The Promised Neverland, and that's a wonderful thing.
Heading into The Promise Neverland's season 1 finale, the jailbreak was finally put into motion. Ray and Emma set the Grace Field house on fire, giving them a chance to reach the edge of farm and scale the giant wall using stolen sheets, setting up a grand, emotional final chapter.
The Promised Neverland anime ends with Chapter 37 of the manga, so you'll want to read Chapter 38 in volume 5 to see what happens next. Though that's a place where you can start, I highly recommend going back and reading from Chapter 1.
From there on, everything she did; including becoming a Mama, giving birth to Ray, and sending off the orphans to become demon food, was the sake of prolonging her own survival to spite the demons from eating her.
If you don't want to wait until 2020 to find out what's next for Emma, Ray, and the rest of the kids, your best bet is to pick up the manga. There are a total of 13 volumes and counting (only nine ...
The Promised Neverland anime ends with Chapter 37 of the manga, so you'll want to read Chapter 38 in volume 5 to see what happens next. Though that's a place where you can start, I highly recommend going back and reading from Chapter 1. The Promised Neverland anime's production team took some liberties with their adaptation to make it ...
The Promised Neverland manga is currently available from a variety of retailers as digital and physical volumes and is also included in the new Shonen Jump subscription service. While the manga volumes are only translated up until volume 9, the Shonen Jump subscription goes far past that with nearly 50 additional chapters.
The whole "the oldest book is from 2015" and Minerva story was done a bit short and confusing in the anime. But can't tell much more because I'm speaking from my memory.
Read from the beginning. It goes by quick and it's worth it to see the slight differences. Also, the inner monologues are absent from the anime, and add a whole other layer to the story.