WASHINGTON — Every two years, the NBC News Political Unit produces a document that we affectionately call “The Book.”

It’s a compilation of everything you need to know about the upcoming midterm elections: The big picture, the historical background, the races to watch and the trends that have defined the cycle.

In it, you will find descriptions of every major race as well as our behind-the-scenes rundown of what to watch on Election Night, hour by hour.

The political battleground this cycle is bigger than ever, with well more than 100 competitive federal races — not to mention some extremely close gubernatorial contests. History will be made in races around the country. The electorate may be in the process of a major realignment. And, as we learned well in 2016, surprises often happen.

So this year, instead of just circulating The Book to our colleagues at NBC News, we’re sharing it with you so that you can follow along with us, race-by-race, on Election Night.