You can joke about it first and ask them to not spoil even in a subtle way? “Wow how could you read so fast! I think I’m going to use up my two weeks :) Also, please don’t share details like that until we meet. It’s not a spoiler but even knowing there’s a twist in the end takes away from the pleasure of facing it in the end! Thanks!”
He smiled as if he wanted to cut his hair really short but in such a way that the back hairs were a bit longer and his mustache trimmed just a little.
Her cheek bones perked up like she could drink her beer in one gulp all the while doing a backflip over two cows.
And various other stupid physical descriptions like that.