I heard in most chess forums this book is for 2400+. Can this book also be useful for Class B players? I'm looking for a book to improve my calculation and planning. If so, in what ways? What would be the best way to self-study this book as a Class B?
I'm rated around 2150 Elo and I used the book two years ago, to solve exercises on the way to work. I could solve approximately 50%, which felt somewhat disheartening, though objectively, I guess, it's pretty ok for my level. I definitely profited from the training.
I wouldn't recommend the book for players significantly weaker than me. Mostly because it's demotivating if you are always struggling to even think in the right direction. I have found that the final instalment of the Yusupov series fits my own level better (i.e. tough but solvable).
But if you can keep your motivation up, even without much positive feedback, of course you can profit from thinking deeply about just about any position.
For a B-player, or any non-master for that matter, the problem with this book is that the examples and study positions are complex and will be difficult for an amateur to understand and analyze. Nevertheless, the concepts in the book and techniques are completely valid and useful for a B-player.
To make best use of a book like this, I would recommend learning the ideas and concepts in the book and then applying them to easier examples which you can find in intermediate-level books. So, look at Aagard's examples, but when you actually go to train use easier positions.
I've read 60 Memorable Games by Fischer, Art of Attack by Vukovic, Understanding Chess: Move by Move by Nunn, and My System by Nimzowitsch.
These books got me to ~1800, but something was missing.
Before the end of 2018, in December, IM Alejandro Moreno recommended Chess Praxis.
"Another book?" I thought. Weary and withered, I reluctantly read the book. I really felt like a law student at this point (mind you, I was studying chess in a quiet area of the law library - with the rollable board and wooden pieces).
I've read Chess Praxis. Here's where it's gotten me:
(Note the highest rating in October - that was when I finished reading the three books listed at the beginning of this post, minus Nimzowitsch. I was playing sharp, but my positional play was unsound. So once I got bored of the lines, I dropped down to ~1700 (!) in a week).
And in my last USCF Tournament (2/16/19), I scored 2.5/4.0 in the open, beat an expert, drew a National Master, and took a 1900 to the cleaners. My rating exploded from 1815 -> 1880.
If there's one book you must read, it's Chess Praxis.
Reading those five books only took three months, but those will be the three most critical months of your life.