Most people in cpk will remove their nicer spell books and use the spells they memorize, or have smaller spellbooks for cpk. It's really not a big deal for most paths, as in most cpk situations you can memorize most of what you need.
To add a bit onto what Thralk said, the equipment you drop is somewhat random (you wont necessarily drop everything), and players will obviously take anything valuable. Some mobs will also loot your corpse, so you need to be careful with those. When you die, you're presented with a nice list of what's in your corpse
Getting cpked can vary in terms of impact. When Im active, I get cpked at least twice a week by mobs (and I spend most of my active time in cpk). On the other hand, I don't think I've ever lost more than a mil in gear to a player via cpk. As a new player, there are very few reasons you should have to go into most cpk areas, and there is no reason for you to take expensive gear into cpk, especially not at low levels. If you're careful, you can mitigate most of the risks of cpk.