What book have you given as a gift most often?
If it's professionally-related (e.g. giving books to people who wrote for me) without question it is Eats Shoots & Leaves, as some years ago I gave copies to all my freelancers. https://amzn.to/2POdCis
@estherschindler It's a great fun and helpful. But, these days my first pick would be Dreyer's English.