An important advantage of ebook readers is their ability to modify text size and page orientation, for the most comfortable reading configuration. The ebook reader has to reformat the text on the fly and with minimum delay. Current ebook readers (e.g.\ Stanza on the iPhone) can do this reformatting, but cannot deal with complicated text such as mathematics. We have been experimenting with using \TeX\ as the formatting engine. Of course it can handle complex mathematics, but it also creates the best line breaks of any ebook reader, e.g. Stanza. We will report our experiments with using \TeX\ as an ebook reader on the iPhone.