picotts looks cool, but it's not maintained (maybe it's perfect already?). nanotts is a fork of picotts with improvements to its cli interface, but it's not very maintained either (I was not able to compile it, due to it expecting Alsa; somehow -noalsa switch didn't help). I also discovered gtts (and the simpler google_speech), both available through pip. They're interfaces to google's apis, and have routines for handling large texts properly.