I am new to collecting but thought I kind of had a idea of what would grade well

I have only been collecting coins for almost a year now and thought my grading ability was pretty good until I sent my 5 coins off for grading to NGC and found out it lacks ability. My question is, is there any books or webpages that any of you can suggest me reading that would help me in this field at all. I was pretty close on some coins and way off base on other coins. I had a o/s vam-5 1882 coin that I thought was a strong ms-63 and it came back as au-58 and another o/s I thought would grade higher that was body bagged but on the other hand I had a 1891 I graded as ms-63 and came back ms-62 so it seems I can get close on some and just miss the boat on others. so any books or webpages that would help would be greatly appreciated.