Hmm, an app with ebook reading features that opens native doc files . . . nope, sorry, can't think of any. Frankly, I'd be surprised if there were, since doc is such a horrible format for storing ebooks (personal opinion
). Especially on a smartphone, since doc files can be quite large whereas epubs of the same work take up much less space. (I am assuming you mean Microsoft Word docs.)
Still, there are some apps that will open doc files; just search "word docs" in the Market, and you'll find several. Docs to Go shows up in a lot of users' lists of apps, but I don't know how well it would function as an ebook reader.
You could also just load the files into Google Docs, and then read them through the Android browser or Gdocs. However, I imagine that would be a pretty poor ebook reading experience.
If you really want the bells and whistles of a true ebook reader, you're probably going to have to convert your files to epub. (I haven't even been able to find a good ebook reader for plain text files, and you would think that would be easy!)
I believe Calibre (a desktop app for creating epubs) will import doc files, plus it has lots of options for customizing your ebook. Sigil is an open-source epub editor, currently in development, and it's looking quite promising as well (
sigil - Project Hosting on Google Code). And some good epub readers for Android include Aldiko and FBReader.
Personally, I would recommend biting the bullet and converting to epub. Most of my ebooks are in either HTML or plain text format, and I'm in the process of converting them to epub, one-at-a-time, as I decide to read it. I've been reading ebooks for a long time, in a lot of different formats, and epub is looking to become THE standard format for ebooks. As such, it is well supported by a large number of apps and devices, and should be relatively "future proof" (or as future proof as any non-plain text format can be). I think it's worth the time to learn more about epubs (as a document format), and the more I'm learning about it, the more I'm liking it.
Just my $0.02 (USD).
Cheers.