There's a lot written about the perfect kind of chair for homeworking - it should be ergonomically delightful, robust, not secondhand (in case it ruins your feng shui balance), etc, etc. But I think this overlooks a basic necessity which is home-like comfort. Since I've had a garden office/shed, I've always squeezed an armchair in there too and I'd recommend this to anyone. If you're looking for one this Christmas, why not ask Santa for the marvellous Bibliochaise pictured? It comes from Milan-based design studio Nobody&Co who quite rightly call it "an armchairlibrary" since it offers 5 metres of bookshelf space. It measures 102x85 h.73,5 cm and comes in six colours (frame and cushions) which you can fiddle about with yourself on their website. They also have a marvellous standalone bookcase called the Piola.
Alternatively you could follow Enterprise Nation's advice who pose the question, what do you buy for the homeworker who has everything? They very sensibly suggest a garden office. By the way, if you post a comment on their site this week you could win a case of Da Luca wine.