Descent II feels more like an expansion pack than a sequel and that's because it's pretty much the same engine with minor cosmetic enhancements.
CD imaged as a bin-cue pair and compressed with OS X zip. Just unzip and burn with Toast to make a CD that contains both game (version 1.2) and audio partitions.
The last download at the top right is an updater.
On the good side, the new weapons are more powerful, the new enemies are cool and the maps are bigger--and now you can go back and revisit secret levels, sometimes from different maps. On the bad side, the Guide-Bot is annoying, the secret levels are for the most part confusing if not frustrating and the ability to destroy lights may look cool but it makes navigation difficult. But all that is nothing compared to the Thief-Bot. This character is so detrimental to gameplay people are still complaining about it in the new millennium (like in this blog post). It would take three years before gamers got the sequel they deserved with Descent 3, but in the meantime Descent II kept the franchise alive and it did a good job at that.