That's impressive. You must be teaching yourself then? I learned the same way through books. Chord changes can sometimes be harder than the chords themselves! That was an interesting statement you made about the comparison between piano and guitar. When you say the guitar is harder physically, do you mean rhythmically? If so, I agree and would recommend a metronome. I think there's even a virtual metronome somewhere online. Did you ever use one for piano? The metro is a mean challenge in itself. I hate it but helps you learn to keep time.