The book that belongs to the HBP

[Tandra]

No: HPFGUIDX 168489

Ok so I'm reading HBP for the 3rd or 4th time and why this just hit me
I have no clue....but seriously how much older than Harry is Snape?
Why is it the school is still using the same textbook one of the
professors would of had in their day? LOL It can't be that much
different in the Wizard world than the real world. A book that is what
maybe at least 30 years old, still being used?! I just find that
odd...no one else on this? :-)

TK