This is a basic, but very reliable plugin

I’ve been using this one for years, and should have left a positive review long before. It may seem a bit worrying that it doesn’t look like it’s been touched in a while. I think the developer should come back and give it a tweak or version update, but really, it still works very good with the latest WP, and it’s really useful for sites where you want multiple authors but not manage giving people their own accounts.