I agree a bookshop would posh the town centre up a bit. But I can't believe it would be commercially viable. Many years ago there was, briefly, a not-bad second hand bookshop in Dartmouth Road, but it didn't last long - and that was before the days of Amazon, Abebooks etc. I'd have thought that the long-established Kirkdale and Dulwich bookshops would between them have mopped up most of however much there is left of the SE23 market.