Thinking about it some more, @PearlCritic, I think the chances of this being an accidental choice are close to zero.
I would be tempted to say something like, "I was just wondering whether you'd read the book you gave us for Isla? Because we were quite, er, surprised by the storyline."
Then if she says she didn't read it, I'd say something like, "Oh, that's a relief actually. It's just not one I'd offer as a gift to someone else's child, given the controversial subject matter."
And if she says she did read it, I'd say, "Right. Well, if I'm honest, that's not how I'd planned to introduce this sensitive topic with my children. I'm sure Isla will come across children who identify as trans at some point in her childhood and she'll naturally have questions, and we'll cross that bridge as and when we come to it, in an age appropriate way. But right now she's too young to understand that boys can't actually turn into girls and vice versa. She hasn't shown any signs of wanting to identify as a boy, but if she did we would respond to that in accordance with the recommendations in the Cass report, which represents current best practice. The messaging in this book seems to run completely contrary to that, and I wouldn't be surprised if books like this were removed from schools before too long."
But then I wouldn't give a fuck about burning bridges with people trying to indoctrinate my kids into their batshit ideology.
💅