Which book should I choose for German grammar?

Hey. I am in the process of learning German, and was looking to pickup a book on the grammar portion of German. I have two in mind, but am open to suggestions.

The two I am considering are Collins Easy Learning German Grammar, and Hammer’s German Grammar and Usage. If you have used either of these and would like to give some input, it would be much appreciated.

If you used a different book and would like to report what you thought of it, that would be fine too.

Thanks for the input.