For those who don't know what Tumblr is, it's a blogging platform which is made to be super simple and enable people to post super quick. I see it as Twitter, but without the character limit and the ability to post text, pictures, videos, links and more in a blog-like format. It's great for people who just want basic options and don't want to go through the hassle of setting up hosting and what not. You can also have other Tumblr users "follow" your blog, so whenever you post it shows up in their Tumblr dashboard.
However, if you're looking for the versatility and options of Wordpress but still want a simple Tumblr-like look, these themes will be perfect to fit your needs. Each theme has been hand picked and are ideal for people who just want a simple blog theme where their content is key.