> I don't think it has anything to do with sales or selling.

It does. Whether you know you are selling or not, you are selling.

> Just be yourself

If you are a natural born salesman, then that works. If not, by all means be yourself anyway, but be aware of what sells and what doesn't, and put some effort into it.

The book which has taught me what selling really is (and why techies often fail at it) is "The art of salesmanship" (I guess that's the English translation) by Heinz Goldmann (sadly it's little known).

Interestingly, Goldmann points out why sometimes skilled and passionate people fail at selling.