There are some apps that offer free e - books which might have Sao light novels. For example, Project Gutenberg. But it mainly focuses on classic literature, so the chances of finding the exact Sao light novel might be slim. Another option could be Libby, which is connected to your local library. If your library has digital copies of Sao light novels available, you can borrow them for free through this app.
One great way is to buy the physical copies. This gives you the pleasure of holding the book, flipping through the pages, and you can build your own collection. You can purchase them from bookstores, both local and online ones like Barnes & Noble.
You can try to find it on some e - book platforms like Amazon Kindle. They usually have a wide range of light novels available for purchase and reading.
Cost - effective. Sometimes online reading platforms offer free or cheaper access to light novels compared to buying physical copies. Also, you can save on storage space as you don't need to keep physical books.