Game Developer was an in-depth monthly magazine designed to expose ‘the art and business of video games’, and was published by UBM Tech (which also runs Game Developers Conference and Gamasutra.com) from 1994 to 2013. 19 Years! Unfortunately, it stopped publication just two months ago… but thankfully the GDC Vault has the whole backlog archived and available for free.
I only recently became aware of the magazine myself, but there’s a great history in there to catch up on of general design talk and post mortems. If you’re going to check out the site, you should also make sure to explore the rest of the GDC Vault. There are tons of free (and pay-for-access) videos of past GDC presentations as well.