'Blurb is not necessarily used to mean exaggerated statements in advertising. It is most often used to just mean short advertisments or announcements mostly of a complimentary nature as well as promotional descriptions like those found on book covers. 'Hype' on the other hand has a more negative meaning as it is used to describe extravagant and excessive advertising as well as something that is deliberately misleading or a deception. 'He says there was no energy crisis, it was all a hype to maintain profits for the oil companies.'

blurb= build up about a product, hard sell, hype= notices, pitch, plug, press/media cover

The answer below is perfect, just wanted to add that "blurb" always means a short piece of writing. Blurbs are never spoken. We mostly talk about blurbs on the back covers of books, but they could also appear in print advertisements. "Hype" is more general and can refer to any kind of advertising and promotional campaign, or even people's general expectations about something.