You can try it over at 3D Bookshop or easier to remember (redirect): 3dbookshop.com
It’s the bookshop experience; but online! You can walk around, pick up books, flip them over to read the back cover, and open them to read a sample or the full book (about half the books are public domain or creative commons).
Your position in the space and the books are automatically saved to your browser. If you’re reading a book, you’ll also be given the option to immediately continue reading on return.
I’ve also spent a lot of time making sure the built-in reader works well. It has a built in dictionary, notetaking capability, a search function, and of course a table of contents. Used Foliate JS for the reader as it reads EPUB, PDF, and CBZ.
Let me know if you have any questions or feedback!

