I See Dead People
In creating story systems for the new World of Darkness, White Wolf Publ. have changed around their approach to the dead (as opposed to the undead). Where you could play a Wraith--essentially a ghost--in the old system, the new thematic equivalent is Geist where you play a mortal whose life is inextricably bound up with dealing with ghosts, who in fact has a spirit bound inside them which gives them some powers in dealing with the dead.
This is a typical World of Darkness roleplaying source book and I believe it would work well alone as well as in conjunction with other World of Darkness books in creating a game of modern horror--in the loose use of the term.
If you're set on dealing with ghosts and the dead in the World of Darkness, then nothing else will do. If you're looking for your first entry into the World of Darkness, this subset wouldn't be my first recommendation.