In addition to the other comments here, many eBooks are available from your public library. If the user is in the US, this includes Kindle books as well. Yes, there's a bit of a waiting time on titles sometimes, but it really depends on how many copies the library has available, and how many users want to read the book.
If you're outside the US, Kindle books aren't directly downloadable, but there are workarounds if it becomes an issue.