I used my meteor developer account to get the free discover meteor book (via the limited time 1.0 promotion I guess), but I thought I did something wrong, tried

I used my meteor developer account to get the free discover meteor book (via the limited time 1.0 promotion I guess), but I thought I did something wrong, tried again and ended up with two copies/purchases. It was free, but seems like a bug. Maybe detect if someone already got a book?