There are many readers for Palm devices.
Depends on the device. I use Docs to Go which is in the T3's ROM and "the Reader" to read EPUB's.
For WM5, WM6(I updated the OS on my iPAQ 211) I use Freda reader.
It works well and reads HTML, EPUB and TXT files.
Many thanks to Jim Chapman.
I convert to EPUB and read on either device depending on how good my eyes are that day. I prefer the way HTML displays but use EPUB for both devices.
The choice is yours.
The Calibre viewer, NOT the main program, is easy to associate with various file types.
I just click on the file and it comes up in XP, Win 7 and Linux.
It handles almost anything but does not display 2 pages at once, or I have not discovered how to configure it that way yet.
Ain't it great to have choices??