In order to answer this question, you will first need to determine what the goal of Reconstruction was. A thing is usually a success if it achieves its goals. Therefore, in order to determine if Reconstruction was a success, you will have to specify what you believe its goals were or should have been. The goal that you pick will have a major influence on whether you decide that it was a success or a failure.
One possible goal for Reconstruction was simply to get the South back into the Union. If that was the main goal, the process was pretty successful. The South was completely reintegrated into the Union by 1877 and it never considered seceding again.
Another goal for Reconstruction could have been to improve and rebuild the economy of the South. Here, Reconstruction was at least somewhat successful. The South’s economy did not become very industrial very soon. The region continued to be poorer than the rest of the country. However, it did start to have a more diversified economy and it did not plunge into abject poverty with the loss of the slave system.
Most people, however, would say that the goal of Reconstruction should have been to change the South and make its government and society more just. In this, Reconstruction failed in the short and medium terms. African Americans did get the legal protections of the 14th and 15th Amendments. They were allowed political freedoms during some of the Reconstruction period. However, those rights were soon taken away. In addition, they were not really given any good way to improve their economic conditions. There was no “40 Acres and a Mule” as many had hoped there would be. African Americans did not get true legal equality for another 100 years and they still do not have economic equality. In these ways, Reconstruction failed.
Thus, the answer to this question depends largely on how one defines the goals of Reconstruction.