I also had a hard time finding softcover books specifically, but I did come across a couple of sites with artists whose work I liked. The first is from a site called Mirabelle Studio:
They used the stab binding for their soft-cover books; I particularly like the one with the map as the cover. it’s something I think I’ll eventually try with some of the maps that came in my issues of National Geographic.
Another site I found was Ailie Snow, whose books were incredibly detailed (and incredibly expensive — this one was listed at $300).
It’s made entirely of cloth and stitch, according to the site. The detail on this and the others is amazing (the site is here: http://www.ailiesnow.com/works/). My sewing skills are rudimentary at best, but I do have bits of fabric, ribbon, and sequins lying around that might end up in book form now that I’ve seen these.