In this paper, we develop the A∞-analog of the Maurer-Cartan simplicial set associated to an L∞-algebra and show how we can use this to study the deformation theory of ∞-morphisms of algebras over non-symmetric operads. More precisely, we first recall and prove some of the main properties of A∞-algebras like the Maurer-Cartan equation and twist. One of our main innovations here is the emphasis on the importance of the shuffle product. Then, we define a functor from the category of complete (curved) A∞-algebras to simplicial sets, which sends a complete curved A∞-algebra to the associated simplicial set of Maurer-Cartan elements. This functor has the property that it gives a Kan complex. In all of this, we do not require any assumptions on t...