Fifteen years ago this morning, the cast of Broadway’s The Book of Mormon was celebrating its opening on Broadway and basking in the glowing reviews.  The show continues today at its original home, The Eugene O’Neill Theatre.  As part of the anniversary celebration, Rhino is releasing a new edition of the original cast album on June 26 on both CD and LP. The Book of Mormon was conceived by South Park creators Trey Parker and Matt Stone.  They joined with Robert Lopez (who had written songs for the musical Avenue Q and would go on to co-write the songs…