I had to restart this twice, once bc I wasn't in a good head space for reading and another time bc the sheer amt of characters at first was confusing.
And listen it takes solidly 150 pages for this to stop being an infodump and move into really good story but when it does it REALLY DOES! I loved the shift and the revelation of additional layers of magic and history. And I liked that pieces and characters I thought the author had dropped, she picks them back up well.
If you're into Arthurian legend you'll find lots of fun stuff here, and as a Southerner I found her descriptions of southern white boys so accurate and funny they made me laugh every time, and I appreciated a fantasy being set in such a familiar setting for me (and somewhat unusual for a fantasy novel)
I'm docking a star for a couple of reasons: 1)there are some plot holes that get shoddily covered by Bree suddenly remembering she has been told stuff by other characters, and it's just not always plausible--honestly all it would take to fix is some character going "oh I don't have time to give you all the lore but here's a handy book on the basics" and then that would easily explain why Bree seems to know ALL this stuff that she otherwise shouldn't 
2)the sheer pace of this story. I think they claim its 6 weeks but I really think the plot unfolds in ab 3 weeks and suddenly Bree is like devoted and devastated over these ppl that she's known for half a minute. I would've loved a little more lead time and world/relationship building, before the high emotion events
But otherwise very good interesting take on Arthurian legend and ancestral faith and connection, and magic and fantasy!