I'll beat Dan to the punch here. The best wood is split, dry pine with lots of pitch in it. It burns hot, but rather quickly. Oak is like hard coal. It burns slow and makes low heat. Pine is "uphill wood", oak is "downhill wood".
If is isn't seasoned and dry, you might as well pack up and go home. We found out that when Eureka ran in Chama in 1997. I had arranged for wood the previous fall. The cutter said he had just cut several several pines and by the spring they should be good and dry.
He lied... If he had blocked and split them in the fall, all would have been good. But he didn't do that until spring when I reminded him about the wood order. The result was many cords of wet wood, that would not burn until it sat in the "drying kiln" (aka the "Eureka's Firebox) for about 20 minutes. We had lots of troubles. Eventually Marvin came to the rescue and trade about 10 cords of dry pine he had for 15 cords of green wood we had.