What do you think?

I just came across this line in a review of a new book; "And if you're a Holmes fan, this book is probably a must in the canon. Dan Simmons delivers personal details about Holmes' upbringing you may not have read before."

And it leads me to wonder; How can anything be important or 'a must' to 'The Canon' of Sherlock Holmes if it was not written by Doyle?

Now to be fair the reviewer did not give good review marks for the book that he was reviewing, but the line  "... probably a must in the canon." I found rather curious.

I am not a big fan of pastiches at the moment. They don't seem quite as fun or even as good now the 'e' books makes it so much easier to get published. And I absolutely refuse to try to keep up with all of the them any more, wheat from the chaff kind of thing.

Here is the review.