That's no way to learn about poison gas used at Ypres!!
A quick glance at my "War Room" picture album in the left-hand margin tells I'm no stranger to books and reading, but like a number of gamers I know, I enjoy having something on while I'm hobbying. Sometimes music is not enough to kept the old noggin occupied while I labor on my miniature legions.
Having the game on the radio or the handy audio book are very good options, but if you can avoid the "Goldfish" effect, so are movies (old war movies for me) or even documentaries. The visual stuff is probably better for the assembly part of the hobby when you can afford a glance every so often as opposed to strictly painting.
For most veteran wargamers and miniature hobbyists, the information given so far in this post isn't anything new, but what might be is a website I discovered over at Anatoli's Game Room. So for some my local gaming friends and others on the blogosphere that aren't aware, there's a great site called DocuWatch that has tons of documentaries steaming about history, war, art, science, and more!
I've only scratched the surface myself, but it's definitely worth checking out, and maybe you might even learn a thing or two. :-)