The good!
I would like to begin by thanking Logos for offering free audiobooks. I downloaded this month's offering, Following Jesus, the Servant King: A Biblical Theology of Covenantal Discipleship by Jonathan Lunde and I started listening to it.
The problem!
The book takes up a whopping 1.84G of space in the webcache folder. The audio files seem to be in mono mp3 format encoded at 320 kbits/s CBR. In my view that is beyond excessive for an audiobook. It offers no obvious advantage, but it takes up way too much space. If you want to download this book to your phone or tablet you will be out of space in no time. Comparatively, Orthodoxy by Chesterton is encoded at 64 kbits/s CBR which still provides very good sound quality.
The suggestion
Limit the encoding rate for audiobooks and, if the apps (desktop or mobile) support it, use VBR instead of CBR.