I'm trying to match the protagonist's rank...

So I'm reading this book, right? And the character in it is a soldier, so I'm leveling up my rank to match his promotions. Isn't the protagonist's promotion speed a bit too fast?? I thought he was a Major, but after 10 pages he became a Lieutenant Colonel, and after finishing one book, he's already a Colonel.... So I stopped reading and just played games, and finally caught up lol Now I want to read the book again, but it's not in the library... Why is this book so popular? It's been like two months, hasn't it? lol Well, I'm off to level up my rank 20000