The phrase "sharper fonts" refers to fonts that have clearer and more defined edges, making them easier to read and distinguish from each other. Full definition
With the new Kindle 3 Amazon has again shown how quickly it improves — We get sharper fonts, faster page turns, double the memory, up to 1 month battery life, better PDF support, and half a dozen more improvements. (dealsagar.com)
But it offers high contrast, a nice selection of sharp fonts and font sizes, and — the best part — it never blanks the screen out at all for page refreshes, which are quick and unobtrusive. (pcmag.com)
As for other E Ink - based ebook alternatives, the Kobo Glo HD offers similar sharp fonts with a screen that matches the resolution of the new Paperwhite and the Voyage — plus it's waterproof — but it's slightly more expensive than the Paperwhite and lacks Amazon's winning ebook ecosystem. (pcmag.com)