Such content if obtained from less than legitimate places could indeed harbor that.
But ebooks and most cell phones are hard to break. Yes everyone trots out proof of concept stuff and you bet the antivirus vendors are salivating over the idea of phone antivirus sales. There are estimates there are 10 times as many cell phones to higher numbers than PCs so the market looks huge.
Now if we can scare consumers bad enough they'll buy.
Since some forms of ebooks are simply containers holding html, xml and who knows what other file types, can ebooks be used to insert viruses or other malicious code into PCs, ebook readers or cell phones?