I read "Black Shield Maiden". What happened was it was near closing time in the library, the flap said it was about an African woman becoming a viking warrior, and there were two authors. That all kept me from realizing who "Willow" was.
The book wasn't bad. The main character is a teen-age girl who yearns after her roaming, perhaps missing, father, whom she takes after. Her village is kidnapped by slavers, but she's "rescued" by a lady viking warrior, only to be made a viking thrall where she meets some fellow Irish thralls. Turns out the lady warrior is the chief's sister and also the warchief, but there's tension as her brother favors a less-capable male warrior. Meanwhile his daughter, the princess, who we first see casting a forbidden spell to try to help the queen give birth, is stuck marrying some old guy choosen by her dad. Her only bright spot is getting her own lady-in-waiting-slash-best-friend, but it turns out to be this sullen angry girl from Africa. That's a fun way for the main characters to meet.
The second half of the book brings in the spread of warlike Christianity among other Viking clans, with the sister trying to ally with the more tolerant Muslims. All-in-all it's fine: there are some surprises, motivations make sense, the bad guys aren't push-overs, and so on. I'd read the sequel, but woudldn't look for it.
Now let's get to that Willow thing. At the library I also skimmed the introduction. Having one is a bad sign. Conan books need them to tell you which of the stories were first published in Amazing Tales and which were finished later from R.E.Howard's notes, where they take place in Conan's timeline, and so on. Regular books don't need that. The introduction for this book said it started with the idea of writing about a strong woman, then morphed into having two strong women, in different ways. That would be interesting if the book were written in 1950, but it's from 2024. I ignored that silliness, until about halfway through when I saw the back flap. It said "Willow" was a singer, songwriter and activist, with a picture of a very young, light-skinned woman of color. I looked at the name again -- Willow Smith. Hmmm... . Oh! Oh no!! This is Will and Jada Smith's daughter! The one who at 7 years old was in a Will Smith movie and at 10 sang a song produced by her parents' friend, Jay-Z. And who I just now realized has her dad's name with an "ow" on the end.
The other author was Jess Hendel. I wonder how she knew the Smith family. I'm assuming there wasn't an Ad. Someone must have known someone who recommended her. Or maybe they met in school. Anyway, she wrote part of this book -- no way to tell, maybe half, maybe less, possibly the whole thing after a meeting with Willow. However much, I'd definitely read a book written by just her.