Re-homing books

Can any one tell me a sensible formula for deciding which books ( if any) one should (gasp) get rid off? We only have so many shelves in our house and a purge is necessary. Actually we have far more shelves than most people do. Not that the house is big, just that a lot of it is shelved. And all those shelves now have books crammed sideways on top of others which annoys me. There are also books crammed next to the TV on the bedroom cabinet and in a wicker basket by my bed and stacked up by the side of the sofa bed and... well you get the picture. Some of them are old quick read paper backs that I will never get to again. The problem is I always think I might. But I never do because I buy books so fast that they pile up and that's the very problem.

The tidy up came when I decided that I needed a dedicated shelf for my new quilting books collection. When I coralled them up from around the house even I was surprised to see that they came to a total of 34. Collected over a period of 30 weeks. With more on order. Those of course I will come back to over and over again. But what to do with the other overflowing books?

I could try and sell them on Amazon, but most have no resale value and some in fact have been unsucessfully up for sale for six months or so. We could put them in the attic. But there are already mounds of books up there. And in fact Dennis, who has lived here since 1993 still has boxes and boxes of books in his mother's loft in N. Ireland.
Charity.
Oxfam has to be the answer doesn't it? After all how selfish is it to keep stuff I don't need when it can give clean water to toddlers? But which ones to give away?

I feels like each one is so special and if you can give one child away - I mean book - then you can give them all away because how do you distinguish? And I am certainly not giving all of them away. (Selling feels different somehow becuase it funds more book buying)

So for now they sit stacked up until someone can tell me how to do it.

Or until the pile falls over and kills me.