To say Xander was astonished would be an understatement; he was completely shocked and for very good reasons.
The first reason was, of course, self-evident and self-explanatory. This book, known as the Book of Life, was broken beyond belief and in more ways than one.
Meanwhile, the second reason was that the Whispher had given him something so broken that he might as well be described as subjectively All-knowing. This was not a tiny gift, but it was a literal life changer.
Why would the Whisper bestow something so valuable upon him? So broken?, yet generally so valuable, especially given that it was made by the generous All-Mother herself.
This definitely left Xander perplexed, but with something like this, a book that would actually allow him to influence the fate of all living beings according to his will, he could easily see through the Whisper's deceit.