I've asked a guy from Reddit to take a pic of the UK Tower of Swallow he received from amazon today:
It seems they did the same mistake in format like for Sword of Destiny before...
There should be smaller standard format only. Last year only Sword of the Destiny was bigger. There was a lot of complains about it so UK publisher re-released it with correct fotmat this March. I don't understand then the format for Tower of Swallow...
I contacted Gollancz by email since they need to clarify this. But based on their contact details, it was unclear where to send possible questions or complaints about their books to. On purpose? So I defined my concern as a website related issue. Unfortunately, I did not receive a single response.
The easiest way of dealing with this, is apparently prodding Gollancz on Twitter. The bad news: we have to wait till March 2017 for the correct sized version .