I yet again do not have much time for a well thought out post, and I yet again have a completely boring section to review. I'm taking this as a sign that God approves of my writing (and anything bad that happens to me is Satan trying to prevent me from writing).
The bible recounts the story of Nadab and Abihu getting killed by God for their unauthorized fire. The bible also says (again) that only the Levites (and Aaron) can go into the tabernacle or touch anything holy. What's the punishment if anyone else touches something holy? Say it with me... Death!
Moses collects more "redemption money" this time 5 sheckels per person (Levite). God sure needs a lot of money. I'm not sure what they need shekels for out in the dessert anyway, so I don't suppose it matters much if they're being robbed of them.
Numbers 4 tells which people should care for which things in/on the tabernacle and numbers all of the people that should do it. Hence the book name I suppose.