Coping with Grief by Mal and Diana McKissock is a good book.
Hard no to antidepressants. Grief is a natural sadness reaction that it is better to work through. It is not the same as depression and watch out for drs trying to push antidepressants. He is not depressed, he's grieving and being low, sad and crying is normal.
I found grief counselling very helpful and would recommend it. General advice though is to wait at least 3 months post bereavement - you need to be in a place to be able to assess how you feel and talk about it so if it is too raw for him it could be too early.
I'd also recommend the Bereavement Journey (look at the At A Loss Foundation) but when I did it, everyone on it was dealing with losses of spouses, parents or siblings. It wouldn't matter in terms of the content as it would all help but part of what is helpful is being with others suffering similar loss so unless he has a group with others dealing with close friends, he may feel a bit out of it or disconnected. I don't know though as I've not done it in his situation.
Basic life rule though is you can't truly help anyone with their grief if it's someone they loved. It's a deep pain that the bereaved has to just get to a point where they can cope with it and only they can do that. DO NOT ever express any sentiments like you should be over it by now whether that is 6 months, 12 months, 10 years, - it takes as long as it takes and people saying stuff like this is very distressing. Remember also that all grief is unique because the relationships with the deceased are different, bereaved personalities are different, coping methods are different so no one can ever truly know what another person is going through.
All you can really do is be sensitive to what they need when - is it distraction, a hug or to be left alone - and be guided by them.