I thought this at first, but there is actually a difference between "a little" and just "little". "A little" is confirming that you know something of him, whereas "we know little of him" is more like a denial.
"What's that guy like?" "we know little of him" vs "What's that guy like?" "we know a little of him." Hope that was helpful :)
I think this is answered already by J__l but...
"Knowing a little about someone" is a positive, maybe you know his name, where he lives, who his family are or where he works, possibly even about what car he drives and what he eats, day to day stuff. It won't extend to where he went to school, what his hobbies are, what he likes to watch on TV, what his favourite music is etc.
"We know little about him" is to to not know very much at all, possibly just his name and where he lives.
Number one could be what you learned from Wikipedia, whereas number two is what a neighbour says about someone who doesn't talk to people in their street much.
I said "we know little of him" which is number 2, I think that should have been correct.
'a little' vs 'little', subtle but important.
Just like in English, in Italian you would need the article: Sappiamo un poco. The difference between "un poco" and "poco" is the same as between "a little" and "little" in English. Like temporalthings said, the former means "we know some things about him" and the latter "we don't know very much."
ok, this is a bit delicate. because in English "we know little" is sometimes a subtle way of saying "we know nothing", and sometimes a way of saying "we know much", depending on the speaker, context etc. is the meaning here the straightforward one of "we know some, but not much", or does this sentence gets different meanings in italian as well?
I don't think that "we know little" ever means "we know much": it can mean "we know nothing" (or more likely, next-to-nothing, or nothing that is particularly useful). It seems to me that "we know little" connotes that the amount we know is less than some optimal amount that would be desirable to know.