Don't rely on books and YouTube when you're starting. Classical instruments require specialised technique to avoid injury and to play efficiently. It's little things like holding your wrists straight and sitting with good posture that a teacher will keep a sharp eye on and that a book can't do. Beginners should at the very least get professional instruction on the fundamentals of how to play and then they can learn songs on their own once they have the mechanics down. They say practice makes perfect, but the reality is that practice makes permanent and you can easily cement terrible habits that might prevent you from improving.