ARM Assembly Language

I've started reading a great book about the ARM assembly programming language. The book can be found on-line here and is a web copy of the same book published in 1987.
Why I'm reading this twenty year old book for an assembly no sane .NET or PHP developer heard about (sure someone did, but the meat and bone of the developer population I mingle in cerentanly didn't hear about it)? The reason is really simple.
I need to learn ARM assembly programming so I can understand the code written in my Operating Systems handbook of the undergraduate Computer Science course I enrolled this year. The book is full with ARM assembly examples how different parts of a system function and I really need to know ARM syntax to fully understand the problem space. The book is of course the venerable "Operacijski sustavi" handbook from FER (2011 edition).
It is not a bed book, but its thick with text which sometimes isn't written well (I'm a published fiction author translated in four languages and published on three continents so I know when something isn't written well, mark me) and requires two readings to understand the rich and very complex sentence structure which could be written more simply if the author actually cared about the reader.