This might be overkill, but I'd advise you to buy BOTH copies of Food For Free - the new photograph-based version, and the original hand-drawn version (though it ain't essential to have one of each).
Why?
The photographic one is obviously more 'realistic' and also gives additional visual information as to the typical local habitat/environment surrounding each species.
However ...
The hand-drawn version has benefits in terms of identification, as the illustrator is able to highlight and/or exaggerate key features of the plant which may not be so clear on a photograph.
With both of them in hand, you really can't go wrong!
G