This is my second review of this book (the kindle edition). The first I wrote in haste while I was angry, and after considering it (and some wonderful responses from the publishers) I wanted to rewrite it.
First off, this was a great end to my very favourite series. I don't think it was quite as good as the previous books, but the final climax was fantastic and I adored the very last pages. There's nothing I can say without spoiling anyone who hasn't read it, so I can only encourage you to go read it yourself!
However - I suggest buying the paperback, or waiting for the US Kindle edition (available in February). As a book, this is a wonderful book. As a product, it leaves a lot to be desired. The UK Kindle edition is riddled with typos and formatting issues (which were the cause of my ire in my original review). There are missing speech marks, paragraphs merged together or randomly broken, random line breaks, missing letters, and every 'fl' has been replaced with 'R'. Every time a sentence begins with a 'th' word ('the', 'that', 'they' etc) the 'th' is missing, too.
I should mention, though, that a member of Orion publishers did contact me, and I have been assured that they are horrified and looking into the problem. Hopefully they will have it fixed soon.
In conclusion - great book. Just, for the moment, go for the paperback.