A lot of Google Books now offer both epub ("flowing text") and scanned pdf ("original pages") versions for download. The scanned pdf versions offer a reading experience that is much closer to reading an actual printed copy of the book. However, there are very few uploads of books in pdf. It would be great if we see more of those in the future.

[NovaPhoenix]

However, there are very few uploads of books in pdf.

Thank goodness for that! PDF, especially scanned PDF (as opposed to True PDF), is fine for magazines and text books. But to read ebooks on my devices, I'll take ePUB every day of the week...

I only ever download pdf for the occasional issue of Playboy Magazine. Otherwise I avoid the format altogether.

If you need the book for some kind of processing or for work, a PDF version might be better. For example, that way you can refer to specific pages, and see how the text was formatted in the original (epub might not always preserve this formatting properly, especially if it isn't well-made). You will also never confuse paragraph breaks and page breaks this way.

But if you just want to read, epub is waaaay better than PDF.