Linen is such a perfect fabric for slipcovers. It washes wonderfully well and gets softer with each washing. These chairs are in my client's master bedroom.
As they were so close to the wall, I had a difficult time taking a picture of the backs. Still, you can see the buttons. In this case, they weren't needed to get the covers on and off, just to add detail and interest. You wouldn't want your walls looking at the plain back of a slipcover, would you?
The side view
Another view of the front
And, last but not least, the original chair. My client has had these chairs for 20 years and they just needed a little updating. Even if you have the world's ugliest upholstery, it is nothing a slipcover can't improve. The one thing slipcovers cannot change is the comfort of a piece of furniture. If you hate it because it is uncomfortable, get rid of it. If it's only ugly or tired looking, a slipcover is the perfect solution.