2.6 done. This is written by the composer for the TV series, who explains in the extras that because he had to watch the series over and over again while writing the music, he had a handle on how to slide this story idea into the middle of the series climax around episode seven with Quill and the metaphysical engine. In that regard it's all very clever and integrates into the continuity well - it's a Class story as opposed to a story with the Class characters in it, which is the case with most of the BF stuff. They have sensibly focused on using Dervla Kirwen to the max with this fourth series, which has helped the quality of the acting no end. As with most of the other stories it relies on using tried and tested sci-fi tropes to make it work, but the pace never drops and the last third is about as good as the series gets.
I suspect it's fine if you like this kind of thing, and the Quill content in this series has made it more listenable than the awkward teen angst nonsense in the third series, but really when it comes to sci-fi listening this just doesn't do it for me. I'd rather go back and watch Buffy again and remember the days when I was more in the target audience, or better still, listen to something based on a TV series I actually like.
I think that means I just have the extras on the DVD to go.