There are two very interesting books in pdf format about Mercosur by Paulo Roberto Almeida that can be downloaded for free.
The first book is titled “O Mercosul no Contexto Regional e Internacional ” (Edições Aduaneiras, 1993). It provides some background information about the foreign affairs in the Southern Cone of South America. And it goes over the fundamentals of the Mercosur. This book was written between the conclusion of the main negotiations of Mercosur and the implementation of the Mercosur. Thus, it provides an interesting perspective on the crucial issues and expected impacts of Mercosur, see for instance chapter 10.
The second book was published in 1998, three years after the the implementation of Mercosur. It is titled “Mercosul: Fundamentos e Perspectivas” (São Paulo: Editora LTr, 1998, 160 p.; ISBN: 85-7322-548-3). This book puts the Mercosur in the context of the century-old idea of Latin American Integration. Also, it goes over the implementation of the Mercosur and the first issues experienced by the member countries. Finally, in chapter 9, the author discusses the relationship between Mercosur and the (now defunct) FTAA-Free Trade Area of the Americas.
I strongly recommend these two books for scholars interested in learning more about the ambitious albeit problematic integration agreement that is the Mercosur (or Mercosul…).