abhijeetsengar-dev/free-book-library ? reverse-engineered prompt

Build me a clean free online book library website where people can browse a collection of books, see cover images, and open each book’s details in a nice simple layout.

It should feel modern and easy to use, with the book list driven from a data file so it’s easy to update later. Include a polished homepage, book cards, and a pleasant reading focused design. I also want a light and dark theme toggle if that fits naturally, since I’d like the site to feel comfortable for longer browsing sessions.

Please make it responsive so it works well on phones and desktops, and keep the code straightforward and organized. Use the existing images and book data where possible, and fill in anything missing so the site looks complete. If you need to check current browser friendly patterns or best practices, look them up online first.