This one seems to be a good choice if you don't want to have to refer the readout code to a book listing :
Innova Premium CanOBD2 with ABS Diagnostic Tool, Model# 3100 | Automotive Diagnostics| Northern Tool + Equipment

I have this one :
Autel AL301 OBDII Over The Counter DIY CAN Code Reader
but you have to reference the P code to an included listing in a book.