"Lights Out" is probably set immediately after the first TV-episode, "Deep Breath".
It is told from the point of view of "Fifty-One", who is a teenage coffee-junkie working on a coffee roasting station (ICRS) you can smell through half the galaxy - absolutely gorgeous. While focussing on Fifty-One, this is not only a story about mystery, murder and coffe, but also about growing up, being afraid and, over all, being different.
I liked this story right away, also the end - giving the Coffee station called ICaRuS a new or rather old meaning - seemed a bit dark to me. Now, after having seen the whole 12 episodes of our new Doctor, this ending fits the 12th Doctor just perfect, and I am amazed how excellent Holly Black had already captured the character that Capaldi has given his Doctor - thinking that she probably had not seen more than just scripts, never full episodes.
I really hope to see, read and hear more Holly-Black-Doctor-Who-Stories, but I would prefer them a tad longer.