I too have TONS of books! DH, DS (now 13) and I are all avid readers. I did swap some of his books on swapmama and some of mine on a book swap site. Plus I too pass books to my friends and my mom. But still they were EVERYWHERE! (and to be honest still are....it's an uphill battle I'm afraid). My husband has boxes, and boxes of books from literally before we married (14 years ago) that in 20 years or so he was thinking he would take down from the attic and read again. He has finally agreed that he can find these books FREE now online! So out they go (as we uncover them amoung the rest of our junk)
To help solve my own addiction, I have got a Fire last Christmas and read about 1/2 of my books on there (that 1/2 less paper backs). My mom has a bag of books about every couple months for me but I look through it now and only take the most interesting 4 or 5 (instead of 15 or 20).
This weekend we were cleaning out the garage (it's a nightmare too!) I had a computer paper box FULL of DSs books he had outgrown. I apparently had tried to sell them at a local consignment sale and these are the books that did not sell....well as much as it pained me to do it, into the Salvation Army box they went. I reassured myself that somewhere out there there is a little boy who will love these books as much as DS did. And I found a HUGE box full of MY books either from a library sale or my mom...they have been there for a couple years so straight to Salvation Army they go too (oh the pain!)
Next up, the countless recipe books and magazines I have laying around! I am going to use my hand held scanner and will be scanning and printing the couple recipes in each book I just have to have and put them in a binder then I will pass the book along to co-workers or my mom