If you’re going to get involved in digital reading you need to understand something about the technology.
PDF – this file will give an accurate reflection of what it captures. So it’s the best quality reproduction you will get. On the downside, the file sizes are HUGE – you’re looking at 12MB instead of 400KB file.
If you are reading via dedicated ebook standards, Kindle (mobi/azw)or epub files (and their variants) you will get smaller file sizes but often more corrupt scans. Unless someone has re-edited the entire content you’ll get repeated errors such as u for n c for e and the like. And often the spacing is random. Frequently the text is absolutely unreadable. Beware of course that some of the digital downloads will have been ‘edited’ for the length of the ‘free sample’ and beyond that… there are some unscrupulous businesses out there remember.
There are also some good guys in the value for money stakes. I should give a shout out for Delphi classics ebooks. These offer real value for money. Sadly, not all unco authors are covered.