Normally when you study something, you will repeatedly go over the relevant bits until you get the answer. In What's My line Part 1, when the vampires were trying to decipher the book, Spike told Dalton to "read it again". Spike was studying Buffy to work out the best way to kill her since it wasn't going to be as easy as he thought it would be in School Hard. He looking at how she kills to see if there is any pattern to her moments eg if Buffy always drop kicked her opponents before staking them, then Spike would see that and know to avoid the drop kick when he fights her.