I have found that Game study is helpful when assisted by a book with explanations appropriate to my level. Fierabras is using Kasparov book which I have the first volume. I love these early game but Kasparov analysis to me is very detailed and geared to a much higher rated player. In some ways there is alot of historical variations given and it feels to me like I am reading a Fritz Analysis.Ideas are in there somewhere but it is tough for me to skip over all the analysis. K is a very concrete analysis kinda guy who has thousands of games in his memory.
I am a fan of study older games in that they are openings I play and the play is somewhat inaccurate (more at my level).
I have these books that tend to be a little easier
for the beginner with Master play and explanation move by move
chess master vs chess amateur
historical perspective with big picture ideas
Masters of the Chessboard by RetiDevelopment of Chess Style by EuweImpact of Genius
I am sure that Fier and Tempo will get some real benefit out of the MGP books.I find anytime I deeply study and analyse chess positions I play better and have much better board vision .This study can be contained within tactical problems or a context of a master game. Just as repetition is helpful in tactical problem I also find that studying a game till it is memorized is of value. Unfortunately I seem to have a limited ability to handle multiple games in memory.