The Eplain macro package expands on and extends the definitions in Plain TeX. Eplain is not intended to provide "generic typesetting capabilities", as do LaTeX or Texinfo. Instead, it defines macro tools that should be useful whatever commands you choose to use when you prepare your manuscript.
For example, Eplain does not have a command \section,
which would format section headings in an "appropriate" way, as
LaTeX's \section does. The philosophy of Eplain is that
some people will always need or want to go beyond the macro designer's
idea of "appropriate". Such canned macros are fine - as long as you
are willing to accept the resulting output. If you don't like the
results, or if you are trying to match a different format, you are out
of luck.
On the other hand, almost everyone would like capabilities such as cross-referencing by labels, so that you don't have to put actual page numbers in the manuscript. Karl Berry, the author of Eplain, says he is not aware of any generally available macro packages that do not force their typographic style on an author, and yet provide such capabilities.
Eplain documentation is available online, and there's also a mailing list - sign up, or browse the list archives, via http://tug.org/mailman/listinfo/tex-eplain
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=eplain