This review is for the KINDLE EDITION ONLY. (Unfortunately it's automatically going to appear on the page for the paperback edition as well, something I have no control over.) And the low rating is not for the content, it is for a major formatting problem. The stories are great!
But the ebook locked up my kindle at a certain point in the first chapter where there is a rather complex chart which apparently was not formatted properly and confused the Kindle somehow. I had to reset my Kindle (Kindle 2 with keyboard) to get it to work again. Then, because I'm the kind of person who just has to see what what will happen, I downloaded the book to my other Kindle (Paperwhite) and it locked that one up as well at the exact same place, necessitating another reset. So that's two completely different models of the Kindle that can't handle the chart.
My advice: if you -really- want this particular ebook you should not even look at the first story (the story the book is named after, The Puzzle Lock) and go directly from the interactive Table of Contents to the second story. Which reminds me of another, much more minor, problem with this edition: the Table of Contents is set up as if each story were an individual chapter in a novel: Chapter 1, Chapter 2, etc. Individual titles of the nine short stories are not given in the Table of Contents.
Better than buying a book and skipping the first story, try to find another collection with the same stories in it. When it comes to Thorndyke, many of the books have been published in more than one place. As a matter of fact, there's a Thorndyke Short Story Omnibus that has all the short stories in one place and won't lock up your Kindle. I bought it after I returned this faulty one.
I gave "faulty content" as the reason for returning this ebook. I hope amazon or the publisher or someone follows up on that.
I love Thorndyke stories and I hate giving out a bad rating but this seems to me to be a rather important issue. So once again, I would like to stress, the 1-star rating is for the formatting problem alone and not the stories in the book. If you find another book with these stories in it, go for it!