Do you read comic books as a grown up person? Where do you find them?
There are some DRM free series around but for the most part I think most series are locked up in Comixology/Amazon and the DC/Marvel subscription services.
I buy one of my series (Saga) from my local store monthly, another from Amazon monthly to read in the Kindle client, and buy collections also primarily on Amazon, but I’ll usually go find a .CBZ format scan of it on google to archive away from Amazon’s DRM…
edit: keep an eye on Humble Bundle, they often do large packs of different series in PDF/CBZ formats!
Also recommend: Gonick, The Cartoon History of the Universe