We recently had the chance to shoot a few questions over to the guys at Football Outsiders, who are the preeminent source for data, analysis, and statistical breakdowns on the NFL. Their DVOA, which “measures a team's efficiency by comparing success on every single play to a league average based on situation and opponent,” is one of the best measures of team success you’ll find.
The Football Outsiders’ 2017 almanac, which covers the upcoming NFL and college football season is a must read. It’s chocked full of neat stuff that you can spend hours, and hours poring over.