Thank you America
And not so much the UK
It seems my work is much more popular in America than in the UK, where I live. :-)
That said, one of the regrets I have about my book is that I was too timid in describing the target audience. I hope it's useful to anyone who's got a solid understanding of Plone from a user/administrator perspective, and who has a solid understanding of web development and a decent grasp of Python. Alas, I think some people have bought the book with no prior knowledge of Plone, and found it frustrating. If so, I apologise!

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A common mistake
That said, it seems these people were indeed not the target audience of this book, they should probably be happier with Practical Plone :).