but only just. Poor, low resolution scan. Reading a longer section hurts your eyes.

The worst part is that there is a shadow of text from the alternate face of each page. This is possibly because of the thin paper used in producing the copy that was scanned. I have paperback copies of all 3 of volumes of these Dover editions which are just fine.
The type is not as crisp as I'd like but this can be fixed by passing the document through the appropriate image filter. The DjVu files seems to have something like this done to them, but they appear pixelated instead of crisp, and it hasn't helped the shadow effect. I'd go for the PDF files for quality even though the file sizes are much larger.
As for the content, you cannot do any better than Thomas Little Heath's commentary on Euclid's Elements. It helps to know some ancient Greek for the full experience, but you suffer no great loss otherwise. Heath gives a very detailed exposition of the document itself, the critical tradition surrounding it, and even some notes on the archaeological history, concerning how the document was redacted from the partial extant sources.
3 stars for the scan
5 stars for the content

Yes, I think it is criminal all the tricks played to degrade the scans to make most unusable to collect tax breaks, but what happens to the quality work? Sold to other corporations?

Bad scan quality, worse than most other books here. Readable, though.