Part of your tax dollars go towards your neighborhood library, so you can’t technically read books online for free via the library since your tax dollars go there, but if you’re going to pay for it, you might as well use it!
Some libraries offer free checkout of digital books, directly to your Kindle or other digital reader. If you’re on a phone, you can also just use an app for that.
You won’t be able to keep the book, and the checkout system will work the same as if you had checked out a physical copy of a book.