What should I understand when someone says "You must be expert with OS"?

Disas_main

As the title said what should I understand from this sentense. I will be more specific, I want to become a malware analyst. And I know that I must become expert with most of the OS out there. But I'm confused what does "expert" means, should I be able to program my own OS or I must be familar with concepts like memory managers, schedulers etc.. This is so confusing for me. I thought to buy a book but I don't now which one, also should I buy one or learn for microsoft academy and tldp. I will be very grateful to anyone how help me to clear the confusions.

NotHackingYou

If you have PluralSight, take a look at the Windows Internals courses by Pavel Yosifovich. I've watch many of them and find them very useful in understanding Windows at a deeper level. I would assume you'd want to understand each OS you'll be working in to about this level.

cyberguypr

Another great resource in this area is Mark Russinovich. His Windows Internals books are awesome. Had an opportunity to talk to him at TechEd last year and left felling like I know nothing about Windows.