Gamma World is the second RPG I ever owned (after Tunnels & Trolls) and has a special place in my heart, so I think Mutant Future is cool.
Malcadon's art is hard to classify. Because a lot of it is simple pencil sketchwork (sometimes even on blue lined paper! Now THAT takes me back to middle school) it has a very amateur, fan-art vibe to it, but if you go through the whole collection you'll see that behind the often amateurish look and adolescent glorying-in-violence-nakedness-and-weirdness is a good grasp of anatomy and proportion, perspective, composition, color, and all kinds of good art stuff. So there are layers here.
As a matter of historical fact, the original Gamma World never had this kind of DIY look -- it was largely slick-as-hell David Trampier inkwork. So putting Malcadon on illustration duty for Mutant Future isn't an accurate homage to Gamma World in particular, but it's very much an appropriate shout out to the late 70s. Malcadon's no Trampier (who is? Tramp was one-of-a-kind) but his work is often reminiscent of David C. Sutherland, for example.
(Note -- when I talk about "amateurish look" I'm trying to be descriptive, not judgmental. I'm talking about a style, not a level of skill. Just want to be extra clear on that.)