This is a little bit more involved than some of the literature out there. While not for everyone, it explains the neurology and immunology aspects of MS very well in layman's terms. I would heartily recommend this publication to the newly diagnosed. In the last year and a bit, I have read up on MS from various sources, gorging on the information within. I am pleased to report that the MS Trust publication had a lot to teach me. I know which parts of the brain have been affected causing my diplopia and nystagmus, for instance.
If it's a more general leaflet for friends and colleagues you're after I would recommend the MS Society's "What is MS?"
If you live in the UK, the MS Trust can send you a copy of MS Explained for nothing. You can also download it for free wherever you are (along with numerous other publications), just click on the link below.