如果是一般疑问句的话就是：Are you going to buy an comic book in the bookstore?
如果是特殊疑问句,问你要干什么的时候是：What are you going to do?
问地点的话是：Where are you going to buy an comic book?
如果是问你要在书店干什么的话就是：What are you going to do in the bookstore?
你可以自己根据题目选择要答的是哪一句,我认为一般问的是第一种.
如对于我的解答有问题,欢迎继续追问：）