Can I send people random stuff?
What kind of stuff?
I'm just going to send a stranger a book that I read a month ago.
That is nice of you to send books to people. Some people will be appreciative of you doing this.
What about people who want it?
If you want to give it to people who want it, try checking out some online apps that encourage giving or asking others online if they are interested. You could always donate to a charity, that way someone who needs it will receive it instead.