Ally The book was kind of boring, but if you want to know more about Teresa, you should read this book.
Millie If you're really curious about how the Flare got started then yes. If it's not important to you, it's not necessary. If you're at a loss for books to read them I would recommend it. I personally liked this book, but I also loved 1 2 and mostly 3. Though I think that harsh reality is a view that James Dashner takes.(kind of unfortunately.) So, my point is that it's not necessary but it does give a little back round.