The New World is a short story that's set before the start of The Knife of Never Letting Go (the first book in the Chaos Walking series). I think however, that you will enjoy this short story better after reading (at least a part) of the trilogy before reading The New World. You can also read my reviews of The Knife of Never Letting Go, The Ask and The Answer and Monsters of Men.
It has been some time since I read The Chaos Walking, which I really enjoyed as a very original and dark Dystopian YA trilogy. When I saw some reviews recently for other short stories surrounding the series, I was reminded I'd always wanted to read this one. You can find it Free via amongst others GoodReads.
I really enjoyed the story. What's going to happen is no surprise for people who've read the books, but the style and Viola really brought me back to the series, reminding me how much I liked it. (Also reminding me I've recently bought another book by Patrick Ness that I want to read soon!) I would definitely recommend this short story (only 24 pages long), I think it's a great addition to the series.