I have read both the books you mention, while they are okay I feel the best way to learn the framework is via the many video and web tutorials. There are a list of these on the Ci wiki http://codeigniter.com/wiki/Category:Help::Tutorials.
If you haven't used an MVC framework before your in for a treat.
i have used codeigniter every day for over a year now. id suggest just looking at a few videos tutorials to get the basic idea. then just code with it, thats the best way to learn
its a great framework, however sometimes while using it, you feel like some things are unnecessary...but when you come back to edit code later on you fully appreciate how it works, the file system is great and everything is kept clean and tidy!