Thanks. I'm definately going to practice each individual mesaure more. So say i start at 50 bpm. I should practice that tempo for a week? Then raise it one BPM each week?
I've worked through this book in it's entirety and the best way that I found for me was to pick three to four tempos and work them. In other words, if you can do it at 70 BPM. Do it first at 40 then 60 then 70 then 75. 75 might be a little sloppy and you might have to slow down to 72. It's OK. You will find that this multi-layered approach is a little more interesting and also a little more like real-life. Another thing that I used to do was vary the tempos by one or 2 points. Instead of always 70 BPM, sometimes it would be 68 or 71. This opens you up to different subtle changes.
Raising by one BPM is incredibly difficult to keep going in the long run. Why should it take you 10 weeks to go from 50 to 60? I agree with the concept of a gradient approach but one per week in like having a 50 mile runway before you take off.
You should finish the book at your technique level and at the tempos you can handle. Once you finish it, put it aside, work on something else for a few months and then come back and do it again, this time being more critical of yourself.
In this way, the student (you) gets some positive reinforcement along the way. Increasing by one BPM a week makes it very difficult to feel progress and you might end up dropping the whole thing.
Also, practice a system for at least 30 minures non-stop. None of this read a page and stop stuff. I used to have all of the melody pages laid out so that I could read SIX straight through without stopping. If you can't handle the thirty minutes then work up to it but don't push too hard and strain yourself.
Good luck, what you are working on is the real deal. Every bit of honest effort you put into this will pay off big time.
Oh yeah, one more thing.... SING!!!