One of the must have books i have every read on Drupal 7, the collection of authors have done a marvellous job. The usual price from amazon.co.uk is around £28 but using the above link you can get it for £19 a saving of around £10.
There are many a book reviews about this book so i am not going to get into this, i have just started reading the book. One thing the book with the link i have provided is a warehouse clearance deal, which means the book is not hot of the press. but i bought from the warehouse deals myself, and i could not see any difference. Advised to check details on the items before you buy.