If you are interested in reading top quality science fiction here are some places where you can find it for the taking. The books are free. The first place to start with is Baen's Free Library. There are a number of fiction and non-fiction books published over the last 20 years by Baen Books.
The second place, with rather more books and stories, is a technology center in Poland which is one of two places online that has full images of all 23 CD-ROMs distributed over the years by Baen as it published hardback books of general interest to readers of the genre.
All told there are well over two hundred books in all types of e-reader formats that work on every device I own. There are books by Larry Correia, S.M. Stirling, David Weber, John Ringo, Eric Flint and many others. In an even more unusual move, the CDs contain the full series of some of the authors' works.
Rest assured, the publisher offers these books for free as a way to entice readers to buy more books. Clicking on the image will bring up the index and you can either copy the entire disc image or download the books you want individually, one at a time.
I'm sure by this point everyone is familiar with calibre ebook management software. It's free, works on Apple and Windows and automatically puts ebooks into the format to match your reader. It's a great way to store and manage all your ebooks on your computer.
There are countless other places to find books, not to mention places like Amazon and Book Bub but I keep seeing all the titles from the Baen CD-ROMs still on the shelves in the local libraries so I know they are of continuing interest to readers. If not you, perhaps you know some young reader recently gifted with a kindle reader who would like them.