The Castle is an excellent adventure. Each stage/step is made of several steps and you can make the adventure you want: more action, less action, more horror/less horror, choose the ending you want – the tools are there, just pick and go.
It’s not perfect – there are minor typos (e.g. see page XX), and there could be more consequences/opportunities for each scene and reminders about the scene overall importance: For example there is a library, which is the key location for most of the approaches. The text could remind us that, for example „if you decided that you want to lift the curse, the library offers this and that pieces of information.”
But these are minor things, and an experienced GM can manage easily.
It took us 5 hours to complete and I rushed the ending a bit, since the group decided to fight the Villain. Using all the scenes it can be easily stretched to probably 8 hours, and with bare bones (4 scenes shoud do it) – down to 3 or 4.
As such, it is much, much better as a starting adventure than “The Caliberi Letters” for one fundamental reason: the story it tells has a beginning and an end, therefore is much more meaningful for the players than the Letters (which is really and intro to a much larger story and players don’t care about its conclusion). If you’re wondering which of the two you should get – get this one.