Perhaps it is unfair to call our times post-Christian, churches have often been sold off and used for commercial purposes, we have examples of it locally - one I know of is a bookstore. Years ago one of my favorite discos in NYC was an old church called The Sanctuary - it was even used in a film for a location shoot - the movie: Klute.
It is rather unsettling however to come across photos of the Dominican church (above), nicely converted into a fashionable bookstore. The location is Maastricht, Netherlands, and so it is no surprise perhaps. It will most likely be a common occurrence throughout Europe as the faith continues to dwindle. There are more photos on the architect's site here. It really is a very handsome conversion, wonderful use of space without obstructing the lovely art and architecture.
If I were rich I'd love to buy an old abandoned church in France or Tuscany.
H/T Catholic Church Conservation