Been in this exact spot and it's less about hunting for free books than it is about knowing where to look that respects the authors. Project Gutenberg is the granddaddy, obviously—public domain classics, perfectly legal, and you can get 'Pride and Prejudice' or 'Moby-Dick' in every format imaginable. But the modern stuff? That's trickier. Your public library's digital collection is the unsung hero. Libby or Hoopla apps, you just need a library card, and boom: new releases, bestsellers, all free for a loan period. It's legit, it's legal, and it supports libraries.
Don't sleep on author and publisher websites either. Tor.com gives away a free ebook every month, usually sci-fi or fantasy. Some authors offer the first book in a series free to hook you, which is smart. And honestly, 'free' isn't always the goal; Kindle Unlimited or Scribd subscriptions feel like a library but for a monthly fee, and they have massive catalogs where you can read a ton without buying each book individually. That's how I read most of my genre fiction now.