I have pointed him to this blog. I hope he finds what he is looking for.
From what I have gather, every pilgrim has their own reason(s) for their camino. And in the camino, you normally don't ask another pilgrim the reason for their Camino, at least not on the first date. :)
I had thoughts too about writing a book on my Camino. But after creating this blog, I don't think I will have much more to add (so far). I believe that there are already too many books written on this. Unless, you are writing it from another angle.
Maybe things will be different after I walk my next Camino. If I do write one, it will probably be in an electronic form (pdf?). We'll see.