A very quick read, understandable for a prequel, but still sad because I want so much more of the meat of this Persephone/Hades lore the author is building. I admit, I wasn't a big fan of the 150-year jump ahead we got in the epilogue because I really wanted to see more of Penelope's development. We never even saw her adapting Cerberus to her side, which feels sad. If there's a Persephone/Hades volume that fills in that gap, I'd love it, but I suspect any book on that lore in the series will pick up after this epiloque.
I did notice the official book 1 of the series starts us with the lore of Zeus, so it seems we left the Underworld to begin the series. Feels a tidbit bait-and-switchy to have me fall in love with these Underworld characters in a prequel, but now they've already have had 150 years of events happen to them off screen at the end and when I begin the series I have a new set of characters to get attached to and wonder when I get to see my original ones again.
I'm keeping it 4 stars because I genuinely did enjoy it, which is why I want so much more, but if I'm speaking honestly - the book 1 of the series needs to be good, or this would drop to a 3 star for the lack of payoff.