I know some people can read and remember different things about varieties to help them remember the varieties. The only one I remember off the top of my head is the 1806 O-109 and O-109A - the without stem variety.
I am not to that point where I can remember varieties and doubt if I will ever get there - I use my reference book at home and I use one at the coin store. There is also a quick reference guide available - never really looked at it. When shopping on ebay I keep the book handy - I validate what the seller says. Or if they did not include the overton number I try to figure it out myself.
I have the 4th edition Parsley book - it works for me and I see nothing wrong with a used book. I am not sure how often they change.
