Because 'book', don'tcha know, now literally means 'cool'.
In the most widely used predictive-text lexicon, punching in 2665 defaults to 'book' before 'cool' (much as 43 goes to 'he' and not 'if' - jeez that annoys me), and apparently (Thanks for the heads up, LB) legions of txtrs out there are just lettin' it ride.
'Book. I'll see you there.''That new guy is so book''I can't believe how book it is that there is a long weekend next week.'
Maybe one day I'll get to write a blurb that's just:
This book is book.
Or even better:
The Urban Dictionary - one of my favourite things on the interwebs - has loads of other meanings for book. Including to 'leave in a hurry' or 'run' ('See you guys, I gotta book.' 'I booked it when the cops arrived.'). But my favourite recent UD find is 'book hobo'. Apparently it's a noun (someone who hangs out in bookstores reading but never buying) and a verb (to hang out in bookstores and read but never buy).
'What did you do on Saturday?''Oh, I book hoboed at Readings for a while and then wandered down to Brunetti for a latte.'
This is my new favourite word for my long-favourite pastime.