This book is great. I would say that it is for beginners as long as they have some semblance of C understanding and spent a few hours (days?) reading up about assembly and machine code topics. These skills take years to truly master and the book starts from the beginning. I think the difficulty of asm is overrated (its not uncommon for young kids to learn this sort of stuff).

I think one of the greatest initial hurdles of being a good reverser is not being afraid to wade through large amounts of disassembly and being comfortable with not understanding whats going on for long periods of time.