We usually read grandmasters' game collections not to improve our endgame or tactical abilities, but to understand chess strategy and planning. Of course, Botvinnik was also superb tactician and a very strong endgame player, so there is surprisingly first-rate endgame and tactical play here than one might think. But that is the icing on the cake. It is in his strategic undestanding that he was heads and shoulders above his contemporaries, and for this reason this book is such a great classic.
First of all, Botvinnik had an incredibly deep and accurate undestanding of which positional factors matter more in a given position: e.g., is it important that White has a double, isolated pawn or not--considering that he has two bishops? Second, he knew perfectly how to create a plan to maximize his positional advantages and minimize his disadvantages. Finally, he was unmatched in converting the strategically-winning position so achieved into an actual victory, by flawless "conversion" of his positional advantage to material, or a mating attack, or a won endgame.
All this comes out very clearly in both Botvinnik's play and his annotations. He makes it look simple: a result of the iron logic and single-minded sense of purposes that guided him throughout every game. The reader will learn a lot about what chess strategy and chess planning are all about, both in general and in particular (e.g., which positional factors tend to matter in what kind of positions).
The one slight problem, which isn't Botvinnik's fault of course, is that this Dover reprint is in desciptive notation (e.g., "1. e4 c5" = "1. P-K4 P-QB4") which might annoy some players. But it is well worth to spend an hour or so to familiarize oneself with this notation even specifically for this book, to say nothing of numerous other older chess books one is giving up on otherwise.
At less than $10, it's a bargain.