Most platforms offer some legal free access, though definitions of "full" vary wildly. Subscription services like Kindle Unlimited or Scribd give you unlimited reads for a monthly fee, which technically isn't free but can feel like it if you binge. Public libraries are the unsung heroes here—their digital collections through Libby or OverDrive let you borrow complete ebooks legally, zero cost, just need a card.
Don't sleep on author and publisher websites either. Many, especially for web novels or serials, host complete works free as a promotional tool. Sites like Wuxiaworld or Royal Road built entire communities around that model. It's not always the latest mainstream bestseller, but the selection is huge if you explore genres like progression fantasy or litRPG. Just check the copyright page; if it says 'free to read,' you're golden.
I got into 'The Wandering Inn' that way, all millions of words available on its own site. The catch is ads or waiting for chapters, but for completed stories, it's a total win.