My grandfather LOVES audiobooks. Many of the lower cost audiobooks come in MP3 format. There are a few windows apps that take these MP3s and convert them to bookmark friendly M4B files, however they are wonky at best.
Many linux script based solutions require the (potentially hundreds) of mp3 files be renamed in a logical order, which is just kindof a pain in the ass.
After dicking around with this for hours at varying points in time, I found a tool that actually works. Well. It’s called ‘abc’ (Audio Book Creator).
You can get it here: http://www.ausge.de/modules.php?name=Downloads&d_op=getit&lid=6