Yeah, I'd have to take a look at the specific font file you used, there might be some trickery with TT instructions or hinting involved somewhere...

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In general, thin full Serif fonts tend to look like crap on e-Ink displays, but the font on your Sony screenshot seems to be noticeably heavier, so, if it's the exact same file, Sony's rendering engine is probably doing something differently. Hence why I'd like to take a look at the font file, see if I can pinpoint what might explain the Kindle's rendering.