There’s a surprisingly satisfying way to read 'Overlord' without skirting the law: buy or borrow the official releases. The English light novel is officially published by Yen Press, so the cleanest route for English readers is their print or ebook editions. I usually grab mine on Amazon Kindle because I read on the commute, but you can also find legit digital copies on BookWalker, Google Play Books, Apple Books, Kobo, and other major ebook stores. If you prefer paper, local bookstores (or big online retailers) stock the Yen Press volumes too.
If you want to keep costs down, check your local library apps like Libby/OverDrive or Hoopla—my library sometimes has the volumes in ebook form, and that saved me a bunch when I was catching up. There are also audiobook versions for some volumes; I listened to one while gardening and it was a fun way to experience the world of 'Overlord' in a different format. Lastly, remember that 'Overlord' originally began as a web serial by the author, but the legal, polished translations are the published Yen Press editions—supporting them helps keep the translations coming and lets the creators and publishers continue doing their work. Happy reading, and tip: buy the special editions if you like art and extras—they’re great to have on the shelf.