Aagaard’s books, especially Grandmaster Preparation: Calculation, are quite advanced and designed for 2000+ players. Since you're around 1800, it might be challenging but not impossible if you're willing to work through it carefully.
If you want something more structured and accessible, try:
The Woodpecker Method (Axel Smith, Hans Tikkanen) – Drills for tactical calculation.
Improve Your Chess Calculation (Ramesh RB) – Step-by-step calculation techniques.
Recognizing Your Opponent’s Resources (Mark Dvoretsky) – Helps with deep tactical thinking.
If you're confident in your current tactical skills, Aagaard's book can be valuable, but if you struggle, start with something slightly easier first.
I have noticed that my greatest weakness is calculation. The only chess book I have read about tactics is Think Like a Super Grandmaster, but in that book, Mickey Adams doesn’t provide a step-by-step guide. While checking online, I saw that Aagaard’s book is good, but some people say it’s tough—probably meant for players rated over 2000 FIDE. I don’t have a FIDE rating, but I was wondering: would it be too challenging for someone rated 1800 here?