Ontario Grasses website

There aren't a whole lot of books out about grasses.
The "Must haves"
Grasses - An Identification Guide
Lauren Brown

This is the most popular grass ID book. It doesn't include all grasses, but it will definitely get you off to a very good start.

How to Identify Grasses and Grass-like Plants
Harold David Harrington, Janet Klein (Illustrator), Ann Steely (Illustrator), Robin Hause (Illustrator)

Other valuable resources

Grasses of Ontario
Dore and McNeill
(out of print)
An Illustrated Flora of the Northeastern United States and Canada
Nathaniel Lord Britton & Hon. Addison Brown (3 vols)
Published by Dover

Definitive set of books on NE North America's plants. Includes grasses, wildflowers, ferns, trees & shrubs. Excellent but scientific. Not for beginners.