I've noticed a few different threads on what Foundation One contains and how far it will take you. I've also noticed people who've followed GB for a while with a few questions. So I wanted to say a few things for newbies like me who may have a few questions stemming from confusions from the original BtGB book.
1) Foundation One has templates for designing routines with incredibly specific progressions as well as definitive set and rep schemes that tell you whether or not you are ready for the next progressive exercise.
What does that mean? There is no guess work involved. If you're new to all this like me, you just do what is laid out. If you've done some and made some headway, the templates and prerequisities are invaluable.
2) The progressions are a tad different from what you would find in the original BtGB book.
What does that mean? In the original book there are some strength prerequisites for levels of an exercise that are not totally explained. An example, in BtGB horizontal pushing exercises progressions are shown without really showing that there is carry over from exercises such as dips. They are shown in Foundation One. Again, this slight difference in information is very important.
Basically, BtGB is a great book and a fantastic reference for where you should aim to go. Foundation One takes all the guess work out of getting from a to b. No more trial and error whatsoever. You have specific requirements to meet and an objective way to determine your progress.
In closing, if you're new to this like me, get it and implement it.