I'm glad nobody was hurt. I've got too many books myself and this as always been the nightmare scenario for me.
Now, to be the wet blanket...
It varies state-to-state and company-to-company, but generally speaking, you need to have specific coverage for collectibles of any sort. This usually includes book collections. If anyone here is concerned about this happening at their own home, talk to your agent and specifically ask about this. Some companies will be able to add additional coverage onto your home/renters policy. Some will help you find coverage with another carrier - there are some that specialize in this.
There are usually very specific rules and coverage limits for stuff like:
---Collections (books, stamps, cards, comics, whatever)
---Art
---Jewelry
---Guns
---Antiques
---Taxidermy Items
In short, talk to your agent and know what is or isn't covered.
Legal Disclaimer: I'm an agent, but I'm not your agent. I'm probably not licensed in your state. The only actual advice I'm giving is that you talk to your actual agent.