I love to play the Marshall against the Ruy Lopez, but even at my level (USCF Expert), most players don't allow it. I find myself using the repertoire from this book in my games about ten times as often as what I use against the Ruy. I haven't found any junk in the book yet, although I prefer quieter lines against the Scotch. Another great thing about this book is that it is not just for players of the black pieces; I find the lines useful for White as well.