Notations 21 by Theresa Sauer, from Mark Batty Publisher.
I was really excited to get this in the mail, I'd seen a few blog posts and it looked great. I'm lucky enough to have a couple of issues of Source Magazine which first sparked an interest in these innovative approaches to music notation, so I new this wasn't a book to miss out on.
It's even better in person. It's lovingly produced on a great mat stock that makes the 'notations' and scores look and feel wonderful. There's a diverse mix of styles and techniques with great insight into why the composer took their particular approach.
Anyone looking at the current trends in data visualisation should definitely take the time to peruse this book, full of inspiration at tackling one of the oldest and most difficult visualisation tasks.
There's a website and the blog also looks good.
Get it from Amazon UK here: http://www.amazon.co.uk/dp/0979554640