This book is the 'principal' text used by, ahem, everyone in graduate courses that relate to stochastic calculus. It is certainly not a simple text, and requires background knowledge in the areas of (at least) probability/statistics and measure theory, too. It is well structured, very readable, and is an excellent second book after reading something more rudimentary, such as Brownian Motion Calculus.
It's a very well written book, but to appreciate this book, one still need a good understanding of graduate level probability knowledge, such as martingale, stopping time.
I took out of 1 star after i read this book up to ch10 twice. It's probably a personal reason: the author really leads me to that far in this book, but when i looked back i didn't feel much left in my head...weird?