Before Christopher died, he basically broke out the Silmarillion into individual story books. Fall of Gondolin, Children of Hurin, Beren & Luthien etc.
So if you read the first few chapters of Silmarillion, then read these individual books, you are in great shape for knowing the grander histories.
Unfinished Tales is also a great little book and very accessible.
There's also a neat encyclopedia book by David Day you can use as a quick reference. Costco is selling em for $20 right now
