Having read a few of Ms Kenyon's short stories in her series I have to say I don't rate them very highly.
It centres on a relatively young Dark-Hunter accidentally meeting his grandchildren and the grief of not being able to introduce himself. It also cameos Simi which is odd because Simi isn't introduced until Book 4 (and this is book 3.6). Since this originally was published as an addition to Book 4 I think this should be labelled 4.5 - but that's immaterial.
Anyway, it was a bit saccharine sweet Christmas schmaltzy for me and I didn't feel that we got any special glimpse into the Dark-Hunter world