Going to be a bit tough to sell 2nd hand books and/or magazines...
Had a bunch of back issues and some books in the shop that I simply could not get rid off. Discounted to below cost, no one buys. Put a box of them labelled 'FREE', still couldn't get rid of them (but someone wanted the plastic bin that it came in). Finally managed to find someone who would take them for free (after a lot of begging, and they wanted the plastic bin so I had actually pay them with a $2 bin to make them take them.) I've given them to clubs but they've given them back (minus one or two items). I did finally get rid of them when a customer who possibly has a hoarding issue took the whole box.
Then a few weeks later someone had dumped a new box of old magazines and books in front of the shop just as I managed to get rid of the last box, and I was like... NOOOOOOOooooooooo! .

what a cruel joke...
Astro books and mags are not something we as nerds like to let go; you always feel like you should find good 'homes' for them... but sometimes you just have to...
List them on the classifieds, hold a garage sale or book exchange and hope for the best, but I thought I'd share my experience with getting rid of old blocks of paper not being that easy, even if they were free... and definitely don't dump them at your local astro shop' doors during closing hours!