I started with Forever, because it’s the most recent and totally comprehensive, but I ended up buying both the 2nd edition and Beyond as well. Really, though, you can’t go wrong.
I’ve been on 5/3/1 programming (almost exclusively) for about a year-and-a-half now, and it’s working pretty well for me!
I hope you find the same thing. But really, @simo74’s right: commit yourself to something and just get after it!
Time + Effort + Consistency → Results