I found this while browsing through a bunch of pdfs i was given, and I need to understand this line...

..."What’s more, the rod can change, upon mental
command, to code a new spell or reveal the codes for a stored
spell."

Does this mean I no longer need to prepare spells? that as long as they are in the rod I can just cast them?
I can't find an explanation on this.
This seems kind of overpowered but it is also the most expensive "Spellbook" I have seen.
If this makes me into a wizard who can cast like a sorcerer, just with more limited spells per day, why doesn't everyone use it?

Thanks in advance, I have just recently been running my own 3.5 campaign and will probably have lots of questions.