While not at all recommending that you attempt to do an author or publisher out of their income, it's worth being practical about these matters.
Bearing in mind what Boxtops has pointed out, weigh up the size of the book - 1000 pages, 50 pages? And also its popularity or otherwise. The publishers of a small almost-forgotten volume aren't likely to consider it worth pursuing - but don't muck with the likes of Dan Brown. Also be brutally honest with yourself - is it really for your own personal use alone and if so why are you using a network?
I'm possibly being ungenerous here and if so apologies and retractions in advance, but this sounds so very like a strategy adopted by some teachers when faced with a demand that they demonstrate commitment to e-learning. ie 'I know - I'll scan the texbook and stick it on Moodle'.
Which is most definitely breach of copyright.