Books, books, and more books...

I have books. Lots of books. Books in bookcases, books under beds, books in boxes, books under tables, books in nooks, nooks full of books, books in boxes in the attic... I was in my office today, which doubles as a gym, and feeling crowded. It's time to get rid of "stuff" and as I look around, aside from the box of manuscripts on the floor and piles of them on my bench, the books are taking over. One bookcase is full of crime stuff; forensic books, books of poisons, studies of criminals and cases, police procedures, etc. Another has art books; painting rocks, acrylics, oils, pastels, drawing, Dewberry, landscapes, etc. The one standing on my work bench has my writing books; everything from the sweet and inspiring Artist's Way to Stephen King's On Writing (he has the heart of a small boy---in a jar on his desk). Moving out to the little alcove we call a library we have books on Celiac Disease, cook books, some collector items, a few fav's we might read again some day, dictionaries(my favorite book!), thesaurus, books on CD's, some Vonnegut's, Koontz, King, Konrath and Corben among others. Moving into the family room there's another bookcase with nutrition books, cooking (Kill it & Grill it), some medical manuals, oops, there's another forensic book there sandwiched between two more Konraths and an Evanovich. Let's not even go into my bedroom where I routinely knock over the pile of books on my nightstand while I'm looking for things. (this is why I can't own a kindle-I'd probably kill it.)
I've really got to thin out the herd. Any suggestions? How do you decide what to toss and what to keep? I mean, really! How can I get rid of something I might someday want to read? And how do I know the next person will love them as much as I do?
Help!