There is an old (well, not
that old but it feels like I started it ages ago, just look at my English
) thread on the subject.
HoME sweet HoME?
I haven't read all of the HoME but I can't recommend everything I've read this far - both volumes of
Lost Tales and
The Peoples of Middle-Earth.
If you want to read something that does not (necessarily?) conflict with Tolkien's published works, the stories
Tal-Elmar and
The New Shadow are very interesting, but sadly unfinished. They can both be found in
The Peoples of Middle-Earth.