Unfortunately, this book is full of errors. I looked up the Biblical references, and 10% of them were wrong, in the sense that a scripture reference was given while quoting a passage from somewhere else in the Bible. I noted several instances of this. From an "author" who makes a business out of public domain books, a little more care should have been taken.
Lumpkin inside the book does say that he has taken the translation of others and put them together for this book, but unfortunately the book's cover says, "A contemporary translation by Joseph Lumpkin." This, in my view, leads one to believe that these translations were carried out by Lumpkin himself. Clearly that cannot be the case, for Lumpkin has noted otherwise inside the book, and Lumpkin is not an academic and has no knowledge of ancient Greek or Coptic. Instead, turn to Elaine Pagels or Bart Ehrman.