I agree that a month may be a bit much, especially as a tourist and that there is so much to see (I've got to get on that, by the way). But if you are going to be here for a month there is enough to do. Tourist stuff should take about a week if you stretch it.

And then if you like hiking and water activities you could be occupied for quite a while.

Then there are excursions to Shenzhen, Guangzhou in mainland China, which is easily accessible (try to get a China visa before you leave your country), as well as Macau (no visa needed).

There are also the New Territories to be explored.

In the end, a month probably is too long but you could definitely find enough to do, and you'll probably know more about HK in a general sense than most people do.