I find it difficult to write anything meaningful about this, largely because I have already read the two books that came after it. Moreover I read them some time ago and I'm struggling to connect this to them.
For one thing, regretfully, I am not a lover of short stories. I find forty- and sixty-pagers too short to contain any real build up of ideas. They give me nothing for my brain to work on. I truly love a 500+ pager where the nub of the idea grows; where the preparation for the main action of the narrative makes one really think, and attempt to prepare for the meat of the novel. I want to think with the author, to see whether my and his thinking concur or not, to discover how he might have fooled me or given a twist to the story that hadn't occurred to me.
Indeed if that build up takes at least two-thirds of the novel, then all the better, since so often many authors don't handle the denouement particularly well. The problem for most of us is that we have one good idea, which in a novel is the major part of the offering: To 'wind down' that idea to a satisfying conclusion is almost another story and not necessarily a part of the originally planned idea. Hence the reason so many readers might say that the story "fizzled".
It's not fair really; writers are pretty special people considering their ability and persistence to actually get it written and published!
What we have here is only a preparation for the two books that follow. It doesn't really say much by itself, except indicate, towards the end, some of the possible reason for the main narratives.
I'm not at all sure it's necessary; I did OK without it. In terms of poundage, it barely adds any weight to the tons of each of those following. Indeed I think this novelette could even risk spoiling the primary first book. My suggestion is that you do not read it..