There are quite a lot of GI books out there and I think the one I used was in the Collins range of pocket books, I did find switching some carbs for GI carbs very useful but you do need to test everything for yourself as like all carbs the GI variety will have differing effects on the individual.
I made changes like Burgen bread and some brands of WholeGrain and Seeded breads for white and wholemeal breads, Basmati rice (brilliant in small quantities) for regular long grain white rice, certain fruits I found better than others like granny smith apples and some other green apples were better for me than most red apples, stuff like that, but
I CANT STRESS ENOUGH THE IMPORTANCE OF TESTING EVERYTHING YOU EAT IN COMBINATION WITH EVERYTHING ELSE YOU EAT.
Test, test and test again, it will take a long time and a lot of test strips but it is so worth it
Good luck