abc - Audio Book Creator

Interface is simple, but the internals suck

1. MP3 files are first converted to wav (on disk), then to aac. Slow, why not do it in-memory?
2. No multiprocessing which is a must have for any re-encoding task. Have 32 cores on your machine? Nope, all encoding is done on a single core. Lame.
3. No control over encoding parameters. Bitrate, channels, sampling rate - you can't even see them anywhere.

Final verdict: welp, it still works (m4b with chapters is created) but slow and inefficiently. Too obscure unless you check the source code yourself. Check out other alternatives, that's not the one to pick and look no further.