Oh, I happen to know a bit about this issue. It's very much not recommended to have long lines of text, as you may already know—because that way the eye has trouble finding the next line when returning from the end of the previous one, and the entire reading endeavor becomes rather janky experience. That's one of the primary reasons that we have book pages in portrait orientation and that newspaper articles are stretched in vertical columns. With this limitation, it would be quite pointless to try “utilizing” the screen area with other elements, since they can't just be arbitrarily hanging around the text.
If you're doing a lot of reading, you would do better by having your screen in portrait orientation. Wide screens are better suited for other tasks.
I'm tempted to note, however, that HTML with a simple layout, again, can technically be hammered into displaying in several columns on a wide screen. You'd probably want/need site-specific solutions if you want to keep the site's navigation. But if you need only the main content, you could use an extension akin to the “reading mode” of Firefox/Safari/Pocket, and override the CSS to break content into columns. (There might also be such extensions around that already have columns built in.)
If you're doing a lot of reading, you would do better by having your screen in portrait orientation. Wide screens are better suited for other tasks.
I'm tempted to note, however, that HTML with a simple layout, again, can technically be hammered into displaying in several columns on a wide screen. You'd probably want/need site-specific solutions if you want to keep the site's navigation. But if you need only the main content, you could use an extension akin to the “reading mode” of Firefox/Safari/Pocket, and override the CSS to break content into columns. (There might also be such extensions around that already have columns built in.)