"Is a GL biography available at a book store?"
To my knowledge, there are two biographies. Both "unauthorized". The first one from 1979 is "Gordon Lightfoot" by Alfrieda Gabiou and the other is from 1988 "If You Could Read His Mind" by Maynard Collins.
They both are good at relating the timeline of what happened when. There are some personal stories, but since his life has changed so much since the 80's, I am not sure the information would shed much light into what he does for fun now. He used to go "up north" and do alot of fishing but I seem to recall that he said in some interview that he doesn't do that anymore now that he has a young family. I couldn't tell you if the books are still available by special order at a bookstore, but the Gordon Lighfoot section of Ebay often has used copies up for bid.
"Maybe GL is
just a private person and doesn't want to spill all his personal stuff around."
I think that is a pretty fair assessment. Although if you ever get the chance to speak to him personally,(and I hope you do, it is the thrill of ten lifetimes for any fan)you will find that he is very friendly and humble and he will show interest in your life. Like you are just two "equal" strangers getting to know one another. And don't forget the guys in the band. They are just as friendly and interested too.
"If it's so-then that is OK too."
It's okay with me too, titan.