I first bought Hubbard's book back in 1997 as an Undergraduate reading Ecology for an assignment involving the identification of grasses. On first impression the book seems quite daunting with it's black and white drawings, small text and complex key. However, after actually sitting down and reading the book properly from the start on features used to identify grasses the terminology, keys and drawings become relatively easy to use. The drawings help a lot with identification with accurate drawings of each species features, which is an aspect missing from every other grass related ID book I've used.
The only negatives to the book are:
The small paperback novel type format (a slightly larger more robust version would be better)
There are a couple of mistakes in the key relating to page numbers where the next sequence of features occur (a minor inconvenience as they are on the next page)
Some of the scientific names are now outdated but the currently used names are also in the book and any ecologist/botanist should be using 'Stace' for nomenclature anyway.
If the format of the book could be updated slightly then it really would be the ultimate in grass identification. Even with it's minor flaws I use this book all of the time as a consultant ecologist and have bought another copy to replace the one I recently mislaid.