Tales of the Sun Eater, Vol. 4 is the fourth and as of yet final collection of stories set in the Sun Eater universe. It's also my favorite, primarily because it heavily features characters from the main series and also feels the most relevant to the main series.

Where the other Tales collections felt more like fluff, filling in the gaps in the worldbuilding and providing context for events that happened between the main novels, several of the stories here (without the context of the final two novels) feel like essential reading. The bulk of the stories here explain what Hadrian's been up to between the 5th and 6th novels, and they're great stories besides. This collection features just 5 stories and they're a bit longer than the entries in the other collections, to their benefit. The slightly increased length gives the stories here some time to breath.

This collection also marks the first point where we get a Ciecin point of the view, which is interesting. It doesn't seem likely we'll see that in the main series. If you're only going to read one of the sun Eater short story collections, I'd read this one.