Having the opportunity to review a new Terry Pratchett book is akin to getting up close to a terminally endangered species; there is that moment of awe and then sadness that this may be the last time you see one in the flesh.
Terry does what in most cases is considered impossible; not only does he persevere through his illness but he consistently produces works that challenge the reader. This is doubly true for his most recent young adult novel, I Shall Wear Midnight.