If you want the cleanest, easiest way to read 'Invincible', I tend to go digital and buy through official stores. ComiXology (now folded into Amazon) and the Kindle store host every issue and the trade paperbacks — they often run discounts and you can snag whole arcs during sales. Skybound (the publisher/creator hub) also sells digital issues and occasionally puts up sample issues or bundles; supporting them helps the creators directly. For a more library-friendly route, check Hoopla or Libby/OverDrive if your library is hooked up — I've borrowed whole runs through Hoopla before and it felt great to enjoy the series without stealing anything or waiting for a sale.
If you're picky about reading experience, use a tablet and enable guided view (ComiXology's panel-by-panel mode) for tighter framing, or grab large omnibus editions on Kindle for a comfy, long-session read. And if you're the sort who loves extra material, watch for omnibus collections and deluxe editions — they sometimes include extras that single issues don't. Happy reading; the early issues still hit me like a nostalgic punch, and the later arcs grow into something massive and rewarding.