Q: Is there a way for a parent to restrict all apps except ibooks?

There is no way to do that.

You can use restrictions to disable many things on the iPad, so you may want to explore those. You could at least keep them off the internet.

This is so sad! with all the configuration that you can do the in the 'restrictions' on the iPad, you should be able to restrict all apps except for iBooks. My 9years old is addicted to the game Clash of Clans and if it is enabled then he can't concentrate to read a book in iBooks or the Kindle app. I'm going to email Apple support about this issue. The more people that request this configuration change the better chances we have. 

This is an almost 2 year old thread.  Things can change with updates.

Currently you can lock the iPad to a single App using Guided Access.

iOS: About Guided Access

Use Guided Access to:

• Temporarily restrict your iOS device to a particular app
• Disable areas of the screen that aren’t relevant to a task, or areas where an accidental gesture might cause a distraction
• Disable the hardware buttons

Thank you very much for this! I googled and search and searched and didn't find this. This will definitely help! Now if they could just make it that you could use Music, ibooks, camera, facetime, at the same time and not allow other apps. But I'm happy to at least have this, thanks!

You're welcome.