A book my parents got me when I was just starting was this one. But I truly don’t remember using it too much.
Like a lot of people here said, there aren’t too many books I have that I learned a lot from. But I learned probably 90% of what I know about SFX from U/Freakmo on YouTube. Her early videos are so great and contain such amazing instruction for the step up from latex and nose and scar wax, to encapsulated silicone.
Your 9 year old may already watch Glam and Gore on YouTube, but she has some good step by step for latex and cotton pieces as well (the most recent prothetic she made to attack to a face mask could be a fun project!).
Every Black Friday, the Stan Winston online school has a year long subscription for all their classes for I think half the price. It might be a little but much for right now, but something to think about in the future!