@eureka:

. For some strange reason, the fcscan (or whatever it's called) search bar command also switches the rootfs rw for no good reason, since the fontconfig cache lives in /var (tmpfs).
@hfpop: OTOH, I can't remember where in the fontconfig chain is the KUAL FontConfig stuff inserted, but it shouldn't hurt, at worse it'll be redundant. To be perfectly sure, I'd uninstall it, but YMMV

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Where did you get Gentium & Libre Baskerville? IIRC, Gentium is manually hinted, and the build from SIL is identical to the one on Google's Fonts Directory, so unless you have a weird export/mod, it should look *roughly* the same (it *is* a bit smaller than other fonts though). It does get a bit sharper (and thus thinner) when hinted with a v38 native hinter (what the SPR FT override does, among other crazy/stupid stuff I wanted to test), so depending on how much Amazon's mangled FreeType, that might not be completely surprising.
No idea about Libre Baskerville, but they're not on the list of fonts I switched BCI off for, even though Libre Baskerville does also embed native hinting.
What I *can* say about Libre Baskerville is that it crashes with Amazon's FT on my K5, so, err, I really can't tell you how it looks without an override

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FWIW, the font in the first screenshot is the Palatino bundled w/ the PaperWhite, not Libre Baskerville. I switched to Libre Baskerville on my Touch, but I don't think I posted a screenshot. The second one *is* Gentium *Book* Basic (not Gentium Basic, which looks great too, but is a bit thinner), though, which is what I settled on on my PW, because, among other things, it handles the no-black-flash ghosting pretty well.