There are already quite a few scrolls that will screw you up when reading it (scrolls of amnesia, danger, ill fate, destruction, monster aggravation... not to mention 95% of cursed scrolls). Also, the IBM guild manual is always labelled "irk gleknow mizk", so to someone who knows that, there will be no further surprises from it whatsoever.
Apart from the tomes of order/balance/chaos (which all have weights that aren't 100s, for easy identification), reading a book has no ill effect, except when your literacy isn't great. Once at 100 Literacy, there are basically zero surprises from reading any 100s spellbook (even cursed ones aren't bad to read, unlike scrolls). Reading UnID'd books is completely safe, whereas you almost certainly want to ID any scroll before reading it (including finding its B/U/C status).
As the IBM guild manual is already ridiculously rare, I see no real issue with just turning it into a book. THAT'S going to be the only way it will ever screw up a player more than once.
(Maybe it might also be a good idea to remove the "IBM" from the item graphic? I'm on the fence with that idea, the letters aren't terribly obvious unless you are actually paying attention to that detail...)