Phil Plait is better known for his Bad Astronomy website and his blog - this book contains a range of explanations of common misconceptions in astronomy, together with debunking of things such as the Moon Hoax. You can probably find much of this on the internet, but if you prefer sitting down with a book instead of starting at a screen, then go for this. You can read it through or dip in. Hopefully you won't find any of your own ideas debunked, but you never know!