In reply to Sl@te Head:
Unless you're selling hundreds of books I'd stay away from selling to professional traders.
A premier post on here will cost £6 and its your perfect target audience.
eBay will cost you more than that and it can be a long drawn out process photographing and describing them all.
Books also have a tendency to go very cheaply on eBay too.
For some reason climbing gear always gets higher prices on eBay rather than anywhere else though.