Linearity refers to the order in which information is presented and read. It can be important in text in forms such as novels and short stories, as well as even collections of poetry and news articles. Some information is pertinent to be presented first, and without it, the rest won’t make sense. Indexes, appendixes, and tables of content help break up the linearity, because the reader is not forced to read the entire piece to get to the information they are looking for. This can be extremely helpful in textbooks or journals when doing research or looking for a particular story, and can save the reader a lot of time so they don’t have to rifle through unnecessary text.
In relation to blogs, I believe it can be read either linearly or not depending on what kind of blog it is, and how the layout is set up. Usually, blogs are reverse-chronological, so any new updates appear first and as you scroll down the page you are essentially going back in time with the reader. However, like I said, sometimes information needs to be presented in the beginning for what follows to make sense. If it is a personal blog or one that has the important information in the first posts of the blog, a lot of the following posts won’t make sense to the reader until they finally reach the page with that informing post. However, due to archives and tools that let you skip around to whichever post you want, it can be easy to start reading a blog from the beginning.
I used to read a blog about a man who lived below two annoying women (Deargirlsaboveme.com). When I found the blog, I was confused about a lot of things he would write, such as nicknames, and random facts. It was easy for me to catch up on posts because I could go back to his first page of posts, and actually read them in the order he wrote them for them to all make sense. After I caught up, I easily stayed updated on his blog weekly back in the reverse-order. Blogging makes it easy to choose whether you want a linear experience or not, and that is a very cool and useful fact.