The very first place i've been in Paris.
My first month in the city, i spend over 800€ in this bar (true story)
It's simple, warm and friendly, drinks are not so expensive (for Paris...). You can talk with every body, people there are open minded and funny (but only because everybody is drunk)
If you're looking for somewhere that has an an excellent selection of artist books then Yvon Lambert is the place to go. Not only that but they sell incredible tote bags, with great straps and nice minimal design that will last you a life time. Out the back is a small gallery space, often showcasing the work of featured artist who's book is for sale in the shop. One of my favourite things about this shop is how friendly and welcomign they are! Not only that but they do cool collaborations, such as the one with David Horvitz, where he emails them a new photograph of the sky every day, the bookshop prints it out and you can only buy that one image on the day.