When I click on the image of a cover, I get a pop-up image of the cover, which makes it easier to see.
But the pop-up is a fixed size, depending on the size of the original image. If I want a large pop-up window I have to download a large image (say 1000 x 1500 pixels). But an image of say 300 x 450 pixels has all the detail I need, IF I can stretch it to full screen.
Now I don’t mind using large images, except that it takes more room on your server, and there is a noticeable delay as the screen is drawn, presumably because the large image has to be downloaded in the background.
What would be nice would be if I could store small images, but that the pop-up is either resizable, or that it shows as a fixed height and the image is stretched to fit.