I agree with JH about keeping them until you are certian what you want to do with the books. I threw mine out in a fit of rage after learning the real truth about JWs. Now I wish I had a few of them back, because they make reference material for here.
Really, the only book I wish I still had is "Listening to the Great Teacher." I liked that pink book. I have a copy of "My Book of Bible Stories," but I will keep it from my daughter because of the violence written in it. I also have the "Greatest Man" book, the Concordinance, "Aid to Bible Understanding," "Reasoning from the Scriptures," and a NWT Bible. The rest of my JW library can be found in the landfill.
I never bothered collecting bound volumes. I told the Elders, "Why do I need them, we have a set in the Kingdom Hall library and a copy machine if I need something." I just never saw the point in having books that I would never read anyway.