The Amazon Kindle ereader app is arguably the best way to read ebooks on your Android phone or tablet, but the one drawback is that you can't change fonts. The default font is pretty darn decent for the screen -- DroidSerif if you were wondering -- yet still has the vital flaw of being a serif font.
For those of you who don't know, serif fonts have the small, curved lines at the end of characters, where sans serif fonts have solid ends. And because your phone or tablet is a screen, sans serif fonts have better legibility (where serif fonts are better for print, like for actual physical books).
So what can you do when the app itself offers you no options to change fonts? Easy: swap the font yourself.
First, you're going to have to root your Android phone/tablet, because Android normally doesn't give you permission to access the area where fonts are stored. To do that, head here, and follow the instructions for your specific device. Tablets should be similar, on the whole, but you should still Google a bit to see what the best method for rooting your tablet is.
Once it's rooted, install this Font Changer app. It requires you to have root access, so make sure to root first, then install.
After installing, you'll have to transfer some files onto your device. You can do that using your manufacturer's file transfer utilities, or you can use something like File Expert. File Expert isn't necessarily the best, but it's free and it's the one I used to do this process on a Samsung Galaxy Tab 10.1.
Now's the time to pick the font files you want (they need to be .ttf TrueType files) and move them to the
/sdcard/.fontchanger/ on your device. Note the period in front of the fontchanger directory. That NEEDS to be there. Now open the Font Changer app and refresh, then it will refresh and import those fonts you've just added.
Almost done! To change the actual font that the Kindle app uses for displaying text, go to the Advanced tab in Font Changer. Now locate DroidSerif-Regular.ttf, and tap on it. Then pick one of the fonts you've chosen -- in my case, I changed it to Roboto, the sans serif font that comes with Android 4.0. (You can get it here). All that's left is rebooting your device, and you're done.
Keep in mind that this changes the DroidSerif font everywhere on your device, so any application that uses the serif font is going to be changed. If you notice this making other apps ugly, all you have to do is go back to Font Changer, find that font again and swap it back to the backed up version of DroidSerif-Regular.ttf.
As always, there's a risk in rooting your device and editing system files (even fonts), so backing up your Android device is a good idea.