We have trouble keeping things picked up, as well, though I am very picky about library books, and they don’t even leave a certain room anymore. I think it’s going to be more work for you no matter what, because it’s an obedience issue (as are most things). Lay out a ground rule, and follow that rule so very consistently. For example, if your rule is library books must stay in the living room, the moment you see someone with it outside of the living room, the consequences kick in. No warning, because they’ve already been warned of the rule. I spank for disobedience, but I know that is different in other families. Whatever you choose, stick with it. They will get the idea after a few days or a week. And then stick with it still! Because this is when they will see if they can get away with it, even just a tad.
I have found this to work better if you are working on all obedience issues at once, rather than one particular specific rule. I have read “Raising Godly Tomatoes” several times, and I try hard to implement that. It has been awesome, when I’ve done it consistently.
When I haven’t, it has not worked, which the author warns of. 🙂