For those people for whom curling up with a laptop is not quite the same as curling up with a book, the fact that 70,000 new books are published in the UK alone every year may pose some environmental problems: that's an awful lot of paper!
Currently not many publishers use recycled paper, although that is something that should be campaigned for, so what options are there for the environmentally friendly bookworm?
First the obvious - use your local library. Public librarys are a dying breed, and should be supported anywhere. If you haven't been to yours for a while, check it out, you'll be pleasantly surprised with what's on offer!
Second, second-hand bookshops and charity shops. Again, fairly obvious, and a good source of cheap and often quite recent publications. Oxfam has a number of specially dedicated bookshops that are a pleasure to browse in. (And you can pick up some fairtrade chocolate while you're there!).
Third, the internet. Ebay and Amazon's secondhand marketplace are the mainstream sites, but have a look at Green Metropolis. It's a book trading site with a twist - 5p from every book sold goes to The Woodland Trust's Tree for All campaign. Most books are at a standard price of £3.75, and most have free delivery. Once you've read it you can put it back on the site to sell on, and you will get £3.00 back for it.
Finally, set your books free (and get books back for free as well, if you're lucky)! Bookcrossing is a global community of people who, having read a book, package it up, add a label inside the cover, and leave it somewhere for another person to pick up and read. Every book has a unique ID which is logged on the website so the readers can track its progress, and the challenge is (although you could be mundane and settle for a coffeehouse table) to leave it somewhere relevant to the book...
Of course you could always just download it from ebooks, but would that really be as fun?!