Sunrise on the Reaping

It's very possible this is the best of the five Hunger Games novels. Not only does it show ways of life we haven't seen before, like the nomadic Covey, but it delves into Haymitch's past and the events that caused him to adopt such a cynical mindset. As a nice Easter egg, the book's epilogue fast-forwards a bit past the original novels to provide some closure and new information. Well worth a read!