The show is revealing much more about the White Walkers

George R. R. Martin introduced the Others in the very first chapter of the first book of A Song of Ice and Fire — and has barely shown them again since.The fast-moving skeletons  don't appear in the books at all. The corpses that the Others reanimate have flesh on them and are slow-moving. The white walkers are a race of human-shaped beings who are extremely difficult to kill, possess superhuman powers, and appear to be extremely hostile toward humans. Apparently there's a lot more of them to come.