I've only ever read the one version, but I thought the Penguin Classic one was a very readable translation and it's probably the easiest to find.
I started reading The Divine Comedy using the Mark Musa translation (link is to amazon, other electronic retailers are available) and I found it to be pretty sound. There are some illustrations, but most helpful are the contextual notes which explain in some detail the backgrounds of the various characters he meets dwelling in particular upon those that are allusions to figures from medieval Florence.
penguin classics, mark musa translation, loads of notes and canto introductions to clarify the things you're reading.
I love Mark Musa's translation.
http://www.amazon.com/Divine-Comedy-Inferno-Penguin-Classics/dp/0142437220/
I took a seminar where we went through the entire poem and used mark musa's translation and i thoroughly enjoyed it
http://www.amazon.com/The-Divine-Comedy-Inferno-Classics/dp/0142437220