I do like these pocket references, they are very good at being quickly read and finding new functionality. I also believe that after you gain experience in a product or language their usefulness diminishes. As TOAD is such a huge product the book only skims the surface, detailing only the standard, basic functionality of TOAD. That said it is a good reference to keyboard shortcuts and functionality for viewing and creating schema objects, listing the output of PL/SQL, creating new databases and all of the options.
At UKP 9 it isn't going to break the bank. I've always found out something new from these types of books, but as I've said before, once you've learnt the basics you are still on your own for the rest of the product.