what is the best user guide for my ipod touch 2nd generation using ios 4.2.1?

I have a second hand ipod touch 2nd generation using ios 4.2.1, this is my first mobile apple device and I want to read up on it this weekend but the guides seem to be for devices running ios3 on 2nd gen or 4.3 on 3rd+ gen, none for 2nd gen with ios4. is there one i haven't found or should I read the ios3 guide then the ios 4.3 guide?