McGraw-Hill's CEO Terry McGraw is obviously very excited that he's been asked to work with Apple on a brand new type of computer, and he just couldn't wait another 24 hours to tell somebody -- he showed up on CNBC today to talk about his company's latest earnings, and he more or less spills the beans, saying that Apple will "make their announcement tomorrow," that the tablet will be "based on the iPhone operating system," and that it "will be transferable" (so anything on iTunes now will go straight on the tablet?).
He also says that they've got 95% of their materials up and ready to run as e-books, and it's not a stretch to think that Apple has made similar deals with other major publishers as well. This still isn't official confirmation of the tablet (remember, it's not real until Jobs is actually holding it on stage), but man, we're about as close as we can get at this point. Watch the whole video after the break, with the Apple stuff starting around the 2:50 mark.