Oh, just thought of this:
Blio, the
free ebook reader app for iPad/iPhone, Android and Windows PC, also has word highlighting when using the Text-To-Speech option. While it is not nearly as customizable as on Read2Go, I suppose that those readers who want highlighting can turn on TTS, and turn off their speakers.
Blio's big claim to fame is that it allows publishers to preserve the original formatting of the book, so I'm not surprised that there are limitations to the font modifications available to the user. As far as I can tell with my limited freebie books, you can't select a different font face, nor can you change to a "night" view of white text on black page. (I'm using the PC version; this may be different in Android or iPad.)
Preserving the formatting does seem to be appropriate in children's books though, as you'll have the text and the illustrations showing on the same screen. And the full color is nice in these books, as well.
Many of the children's books include professional narration, and some also include a Blio feature called "guided zoom" which magnifies the text and outlines your current paragraph, which may help some readers maintain their place. I didn't see these features in too many adult books, though.
Blio is associated with the Baker & Taylor store; they've been big library suppliers for years, and the Blio website claims that B&T is the largest book distributor in the country.
Blio can handle imported epubs and xps files. The iPad/iPhone version can also handle PDFs. If the magnification function works the same in PDFs as it does in books, it might be a great option for these. I'd be curious to know if anyone's tried reading PDFs in Blio?