A quick note about the font
Gentium.
I checked the font homepage yesterday, and I noticed an update that might interest some people here: there is a new version of
Gentium Plus Mali (
24 jun 2018).
Gentium Plus Mali is a variant of
Gentium Plus with a tighter linespacing. It has many many characters but no bold (note that your Kindle is able to emulate a form of boldness even if the font has no bold variant).
Gentium Plus Mali is available here:
http://software.sil.org/lcgfonts/download/
If you prefer a native bold and bold-italic variant, you need
Gentium Basic 1.102 (10 Dec 2013) available here:
https://software.sil.org/gentium/download/
This set has less characters than Gentium Plus Mali, but enough for english readers.