Based largely on the good Trip Advisor reviews, I booked a table for dinner at Le Bicorne for a party of 4 about 4 weeks prior to the dinner date. I booked directly with the restaurant by email and received an email confirmation, again from the restaurant's email address (with the rider that they would only hold the table for 10 mins after the booked time of 8.30). We arrived at 8.25 to find the retaurant very busy. The lady who seemed to be running the front of house advised that they were full and made to turn us away. I replied that we had a reservation and showed her the email confirmation. She said that she was very sorry but there was nothing she could do. I asked if I could speak to whoever was in charge and she went over to what I assume was the kitchen and a man in chef's clothing looked at us from the doorway, shrugged and shook his head. The lady returned to confirm that there was nothing that could be done.
So, that is the risk that you take if you try and eat at Le Bicorne - fortunately, we went over the road to Le Galion which was able to find us a table where we had the most delicious meal with excellent service (see my review under their name) and I therefore strongly recommend anyone considering a restuarant in Etretat to ignore Le Bicorne and head for Le Galion!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.