I don't think you will have hard time to find any information about anything in Paris online or in travel guides so it is pretty waste of time to write long, general hints about the city. Instead of that I want to give you some destinations I ended up accidentally or with friend's recommendations which built my own Paris experience in my past visits.
This small bookshop on Quai des Grands Augustins between Pont Neuf and Boulevard du Palais is specialized in original litographs, prints and old books especially about gastronomy and travel. The owner is always there and ready to help you if you give him the expression that you are aware what you are looking for. The place is definitely not for ordinary tourists looking for Paris souvenirs and he wants to make sure that you are qualified to see the good stuff. The real treasure he has is not on display. I found there the most beautiful Jean Cocteau and Miro prints I have ever seen with really reasonable prices.
If you are looking for a place in Paris with good food and wine after 11PM Le Tambour is the place you want to be in. The restaurant is in Le Halles on 41, Rue Montmarte. The waiting staff is funny, the decor is cute, the place is always crowded. Perfect place to end up after midnight and having a real meal. The kitchen is open till 4AM in the morning. Duck confit, foie gras and steak tartare are delicious.
If you have any interest in whisk(e)y this place is a temple for you. I literally lost myself and forgot in which city I am, how much time I spent or how many bottles I stared at for hours and hours. The shop is on Rue d'Anjou and open pretty early in the morning if you plan to spend long hours there. To be honest before I go there I thought it is going to be much bigger but the amount of different expressions they carry is jaw dropping.