To learn to read spin, try focusing just on the contact period - ignore the rest of the motion. Imagine taking a mini-video of the split second of contact. If you do this regularly, pretty soon you'll be able to isolate in your mind the actual direction of the racket at contact. From that, you can read the type of spin. You can also read spin by the way the ball comes off the paddle, travels through the air, and from both bounces on the table. Imagine how the spin will affect the ball, and figure out what to watch for.