There are lot of sites across the internet which solely concentrate on a particular topic and some other spanning over multiple topics without any clear niche boundaries.
The bounce rate is differ for both these types of websites. In the first case the website which regularly publishes very good content will be referred by search engines for the specific queries in the niche. This would result in more frequent visitors turned from search engine referrals.
In the case of websites which concentrates on multiple niche, may not able to satisfy all the visitors equally with respect to the interesting contents. The only way out to retain those visitors is to properly group important articles in each niche such that it can be accesses from most of all the pages.
And, do not worry if your bounce rate even if its is too high, here is a very good blog post from kichus which tells, how you can use bounce rate as a metric to improve website performance.
Checkout the article about the ways to become number one in Google search results.