Interesting games, but Spielmann tends to bog down in vague considerations not grounded in concrete analysis. Also, he seriously overestimates the attacker's chances in many positions, and several times this irretrievably mars otherwise sound analysis.
It's probably best to look upon this as a games collection rather than a textbook. There are indeed some great games here (I particularly liked that one against Bogoljubov where Spielmann's queen ends up on b1). As an instructional manual it's not of terribly much use: just some tedious discussions of classification and whatnot, during which Rudy unfortunately manages to indulge his penchant for being very pedantic indeed.