Nicely done! We've been using a very similar setup at the Dutch public library for the last many years - e.g. https://www.bibliotheek.nl/catalogus/titel.2630729

Nicely done! We've been using a very similar setup at the Dutch public library for the last many years - e.g. https://www.bibliotheek.nl/catalogus/titel.263072924.html/the-confusion/ https://www.bibliotheek.nl/catalogus/titel.263072924.html/th... - complete with thickness based on number of pages (though only in three steps) - but it took a lot of tinkering to get the CSS down to something relatively clean. Great job making something like this accessible to everyone with a handy tool like this! One trick we're using which you might care to copy over (and improve upon) is a linear gradient to fake the pages. I think for thin books, I prefer your white version, but for thick books, it feels pretty sterile.