Full disclosure: I've only read the series I've followed start to finish, as each individual section potentially contains spoilers for the series in question. These include: The Wire, Buffy, 24, Friday Night Lights, Breaking Bad, and Mad Men. (I'm still in the middle of BSG. Really need to get back to that.)
However, for those shows, Alan Sepinwall delves into the history of each series and the people involved in getting it off the ground, generally from origin to present. For The Wire, for example, he covers how David Simon's and Ed Burns' association, and how each of the series they'd worked on--notably The Corner and Homicide--helped build into being able to release the show in question. Using interviews and quotes with the people in question (or archival quotes when certain people, generally from showrunners who are still in the middle of production, are unavailable), Sepinwall's essays create a vivid history--undoubtedly mildly rose-colored but still authentic--of the production of each of the series, and he very clearly defines what he believes makes each of the series listed so important to how television is viewed now.
Each essay is self-contained, thankfully; while other shows are discussed in each chapter, it's typically used in a historical context (as a lot of the show creators involved worked with one another previously) one can avoid most spoilers for a series by not reading the chapter involved. This doesn't work for all of them; there was a mention of a character death in The Sopranos, but without context I can't figure out how important it is. (The book may take for granted that one knows about most of the plot points in The Sopranos.) Aside from that, however, the chapters I read were limited to coverage of the shows themselves.
Sepinwall makes a good argument for the shows listed as to how they've influenced modern television. I can't argue that it manages it 100% (one of the arguments for Friday Night Lights was the DirecTV distribution deal that came with the third season, and Sepinwall acknowledges that it was previously done with the NBC soap Passions) but his arguments are worth reading anyway just to hear the industry side as to how a lot of these series managed to be so successful (or survive by the skin of their teeth).
If you're a modern television enthusiast, you owe it to yourself to give this a read.