Yup you need Flash, as the images are all tiled to allow you to zoom and pan around the pages.
Zoomify (the package that displays it all) now do HTML5 code but its not going to be the easiest job in the world to convert as they have altered the files that define everything
I did a screen shot on laptop, saved it as pdf and blue toothed it to tablet - long-winded but the zoom quality in pdf reader is acceptable enough for me to work with when I take it to van to do the job.
Why be the same as everyone else when, with a bit of effort, you can be different?