Hint 1
Hint 2
Hint 3
Hint 4
The first time you go to the City Post newspaper office, the receptionist very rightly won't let you in, and she gets upset and suspicious when you suggest that Jeremy is dead. You're not official, are you?
After you find out what happened to Jeremy --
How do I find out what happened to Jeremy?
-- go back to the City Post to find that the cops have informed them of Jeremy's death. The distraught receptionist will now let you in.
Take the notebook and click on every paragraph to hear her summary of their contents. Now go back to Jeremy and give him the notebook, or try to.
How do I find out what Jeremy was working on?