I'm a disciple of The Book. I use it each year, with success that is surprising to me. It's like having a coach. Just about every question that might come up is answered therein.
Definitely read the chapters, but get it right away & begin to do the workouts.
Part of the program is also recognizing that nearly nobody ever is able to do every single workout, so yeah, you gotta niggling thing for a couple days here, a trip out of town there, life happens over 18 weeks ! The book is almost a lifestyle.
Those programs are all laid out for you, from the most basic "finish the race" level @ 50 mpw right thru much greater mileage. Go much beyond this book's scope, and you would probably be wise to actually hire a real coach.
The book is awesome. Get it.
Also, yeah, the mid-week "pretty long run" can be daunting. Sure you can run 15 miles on Wednesday, you just 20 miles on Sunday. (that stuff brings the freaks right out of my head - can I really finish this run ? The entire program pushes me right to my limits. I love that.) Sorry about that - was I thinking out loud again ? I gotta get out the door to do my Pfitz run.