Originally Posted by jswinden
Deleting the whole CSS file is risky. I've seen a LOT of ebooks that were formatted in ridiculously convoluted ways, mostly because whoever created the file converted it from another format like MS Word or some other non-ebook format. I've seen ePubs that had one <P>
tag and hundreds or thousands of <br />
, and <div>
tags. If you delete the CSS from a book like that you will probably have a difficult to read book.
It depends on your time and goals. The best thing about calibre is that it is easy to work on duplicates of the original epub so that if you don't like your new book, you can always regress.
Many of the publisher css files are very poorly coded and I have seen some with literally hundreds of font references. Further, not everyone has the skill or time to mess with the css and wants a quick and easy way of dealing with the file. If you have a standard css override in calibre (ie: a few font-face lines and p and div line) then the formatting of the book is just fine if you delete the original css file. Your example of the MS Word file above in my mind is a perfect example to delete the original css file.
In the end, everyone has their own level of perfectionism when it comes to their ebooks. Some don't care if the the PDF they converted has awkward line breaks with page numbers and author name stuck in them and others want every book to have the best, perfected coding that takes care of every little detail. It would be ideal if epub coding was better standardized.