De-cluttering My Books Is Surprisingly Painful

I don't, generally, form sentimental attachments to "stuff." Growing up in the nomadic way I did, you'd think it would be the opposite. But no. "Stuff" doesn't mean much to me. I have only a few physical items from my growing up years: letters from my family, some of my better artwork, five expired passports, a piece of Kolonyama pottery from Lesotho, and a leather jewelry box from Ougadougou that got stained by a green marker in one of our moves. I have kept only a shoe-boxed size container of the girls' baby stuff I can't part with.

I'm a ruthless purger. If I don't love it, and/or it's not performing a function, out it goes.

But not when it comes to books. I have a hard time letting go of books, except for those I didn't care for. I have a theory about that. Books were the one constant -besides my family- of my nomadic life.  They were the steady friends that never failed me, bringing comfort and pleasure.

But my shelves will only hold so many books. So it's time to purge...I guess. Either that, or buy more bookshelves, which Todd's not thrilled about. I'm not either, since it means I'll have to put them together.
Theoretically, I don't believe I need to keep every book I buy. And just because we homeschool doesn't mean we need a house full of books...does it? See, here's the problem: that sounds like a great idea to me: a house full of books. Bookshelves as functional decoration.

I've been working on book purging for over a month, but I'm killing my effectiveness with my waffling.

Do you have regular book purges? Any ideas on how to get over my dread of missing a book after I get rid of it?