Kindle! A Princeton study entitled "Fortune favors the bold (and the Italicized)" (their emphasis) has shown that readers retain information more reliably when they are challenged with so-called "disfluent" fonts (like the top one above). This flies in the face of the belief that easy to read text is easier to remember and should give typographical titans something else to ponder when placing text upon a page character by character.
Now, what does this have to do with e-readers? Most are stuck with standard fonts that cannot be changed and fall squarely in the "fluent" category -- they're so easy to read your brain spins down. The solution is, of course, to add more and broader font support to the devices, something we'd love to see regardless of scientific merit. Until that comes to pass try holding your Kindle at odd angles or squinting. Maybe that'll help. Or, you could just put down the Proust and pick up some Clancy.