Ripping a DVD is pretty straightforward, if a little dull. Ripping a DVD collection is a bit different. Instead of doing something in the background for half an hour or so, you're looking at an ongoing job (or collection of small jobs) that will probably last for weeks. So, you probably can't be bothered to do this yourself.
But if you like the idea of your DVD library being stuff you could play on your phone/tablet/laptop on the go, then this post is about the sort of things that you will want to consider in advance before you get started.