Terry McGraw, get thee to media training! Speaking to CNBC Tuesday night, the McGraw-Hill Companies CEO appeared to let slip several new pieces of information about the highly-anticipated Apple tablet.

He confirmed the device would be based on the iPhone operating system, and that it would double as e-book. (And – though the tablet is arguably the worst-kept secret in technology history – he confirmed the launch of the tablet itself. Apple's invitation coyly says only "come see our latest product," but when CNBC's Erin Burnett asked him whether McGraw-Hill would make its textbooks available on the tablet, McGraw responded: "They'll make their announcement tomorrow.")

McGraw was being interviewed about the company's fourth-quarter results when he seemed to break Apple's notorious omerta. (To see a video click here – it's about minute 2:50).

Asked by Burnett about McGraw-Hill's links with Apple, he said: "Yeah, very exciting. Yes, they'll make their announcement tomorrow on this one." So far, so anodyne.

Then he went on to say: "We have worked with Apple for quite a while – the tablet is going to be based on the iPhone operating system, and so it will be transferrable. So what you're going to be able to do now... we have a consortium of e-books – we have 95 percent of all our materials that are in e-book format on that one – so with the tabloid you're going to open up the higher education market, the professional market. The tabloid, the tablet is going to be just really terrific."

(At least he didn't let the name slip, calling it both a "tabloid" and a "tablet.")

If it was a flat-out gaffe and not part of the campaign to build buzz, then Apple founder Steve Jobs – he of the flamethrower-like temper – isn't likely to be thrilled that a content partner has put a crack in the tablet secret code. Jobs calls himself a "big bang guy" – building anticipation to feverish levels as part of the marketing game.

Other people unlikely to be happy about McGraw's comments: executives at Amazon and Sony, who make their own e-book gadgets. Industry experts speculate that sales of the monochrome, button-operated Kindle and reading devices like it will plummet following Apple's expected launch of a touch-screen, full color tablet.