title_body: Full text feed content to Epub
upvoted_answer: In my impression, the main problem is that RSS is usually valid RSS, and the external full text isn't usually valid XHTML, so only browsers with complex parsing engines are able to make sense out of the latter. As most of web documents (websites, HTML) are seriously broken, it's quite hard to read them with a simple implementation. If you have a specific example, one might look into what the problem actually is.