I think the key part of the guide is that it is incredibly readable to the average person, there are some "math" examples but they aren't scary.
His basic advise is pretty simple and easy to follow, put as much money as you can in TSP if you aren't maxing it out add 1/2 your step and grade raises until you do. Don't just put it in the G fund. He stress that if you do this no matter what you will be on pretty solid grounds when you get to retirement.
He also has good general info on things such as sick leave and your pension with charts. It's because of him that I feel once I get my S/L balance up to a year I'll be more likely to call in sick at the first hint of sickness. I'm only going up to the year for a catastrophic illness for myself or a family member so I don't need to carry short term disability. (I'm at something in the high 30 weeks right now so don't feel the need to carry it.)
I also think he's actually the person who lead me to Mr. Money Mustache.