Once you teach AI the correct way to say things, does it remember for future books?
I also think it would be a good idea to make one or two fast versions of each book using a very high quality means of doing that, since the devices people use may not have fast playback capability, or can't play back fast without significant deterioration in quality. It's a balance between CPU specs, playback quality, and recording quality, also considering the final bitrate you need to keep the quality good without being too big of a file size. There's a trick to it since I've heard some really good 64kbps mp3's at normal speed, and some comparatively bad 128kbps mp3's. Some programs can do batch editing, so you can select a whole collection of files to edit or convert.
Some experimenting may be needed to find ideal speeds that will be practical.