I need your help figuring out where to start ?

Hello, sir/madam,

I need answers to two questions:

1. What is the chronology of the Warhammer 40k books? I'd like to start with Warhammer by understanding the lore. I know about the Necrons and the Marines (Space Marines, Blood Marines, Dark Angels) and the Sisters of Battle.

2. Since I'm a beginner, what video games would you recommend for starting out with Warhammer 40k? Please note: no free games, only real, interesting, paid games