Our library also has a connection with a system called Tumblebooks, which is semi-animated versions of kids books that are read aloud as each word is highlighted. We've gone through lots of those. Some books even have attached learning games and coloring pages. It's a little hard to sort the books by age group, and occasionally one of the reading voices irritates the heck out of me...but overall a good option.
Then, I ran across a company called 'We Give Books' (the link here).
These are online books, but unlike Tumblebooks, there is no animation or sound. So it's basically a way to virtually flip through books. And the best part: for every book you read to your child (or your child reads for themselves), they donate a book to a charity that you get to choose. When you get to the end of a book there is a button that appears saying 'give a book,' and Bella likes clicking that button. There aren't a ton of books, but we certainly haven't read them all yet, and there are many recognizable titles. They even have the Skippyjon Jones books, which we love (see our post here), so we've gotten to read the ones that we don't own. And I get to teach Bella how we're part of a global community and about caring for others.
So check it out!