People staying in Paris seem to know that Angelina is a good option for coffee, tea, pastry, quiches and light snacks within a gorgeous, Belle Epoque ambience. So, it is quite popular.
If you are near the area, walk by and if there is no queue enter without hesitation. Have a hot chocolate and a croissant or a tea and a pastry and you are set. That would be an ideal situation.
Chances are though, there would be a long queue in front of this one. Not sure why people don't book to avoid the lines. You could also grab something to go and have a picnic somewhere in the Parisian outdoors.
Keep in mind that pricing is on the heavy side.