Multi-column plays poorly with mobile user agent UX, because the swipe motion made (often with just a thumb) is inaccurate. Works alright if you can reduce it to just the y-axis, but you ask a lot of your end-user on a mobile UA to scroll horizontally also. Flipbook or vertical scroll are the two metaphors that work here.

That having been said, you should be able to tune your stylesheets to vend one that gets users single-column text on mobile devices with some elbow grease. Up to you whether it's worth it.