The answer is yes there a 5th book for twilight based on the original 4 books from edwards point of view but no it is not published because someone leaked some of the chapters to the public when steph was writing it. So now she will not continue writing the book until all the publicity has died down about it.Although she did put on her website the first 12 chapters of edwards version of twilight called midnight sun which can be seen on a pdf file on this link
link
another of stephs book u might want to read is the host which is published and available at all stores stocking twilight series