I buy Crushing the Cup and Triple Crown Handicapper every year. I like his recaps of his previous years. It helps me jog my memory of what I did right and wrong last year, and the stats are a great reference. The online appendix has just about every kind of stat you may be looking for. It's worth the price for me.
Another good resource I use is the BC Stats here:
http://stats.breederscup.com/?_ga=2....974.1535153035