Is this a good start to my book?

I think it's already okay, just some bits here and there, but it can be fixed later on. It's quite fast paced but it's fine. Overall the story's great! I'd definitely read it :D You can show it to others, like family, friends, etc., when you're done and listen to their comments (sometimes you don't have to listen, people have diff. tastes) and reactions. Let them ask questions so that you'll know what parts are missing. Well, good luck! and keep on writing. :D