The antique book fair is set up until early December, then it will be replaced in mid-December by a Christmas market.
The regular buskers are out and about - according to one of the other students at my school, in December there are people out singing and playing Christmas music - but it is still too early for them. Of course, the temperatures in the high 60's at 9pm do not give the city a real Christmas feel to me.
The one Christmas thing that is open and operating is the Nativity market set up right next to the Cathedral. You can buy every imaginable thing you would want to include in your nativity - even if you wanted to do a complete setup of Bethlehem and the surrounding villages...every imaginable animal (including peacocks), person (from shop keeper, to baby Jesus), food (loaves of bread to bunches of grapes), building type, and on and on. You can even buy individual roof tiles to make repairs to buildings....
There are a few stores advertising Black Friday sales for next week (my intercambio partner asked if it was called black Friday in the US because everyone got up in the middle of the night to go shopping) - it is just one more way that we see the US culture creeping into Spain. Here however, the sales are much tamer - no special hours or stampede worthy prices that I have seen - just another reason for a sale.