I really think that writting in books is a completly different catagory than kicking them around. Writing in books (assuming that they are yours, of course) is how you claim them.
Mind you, I have an English degree and love nothing more than the sort of really close analytical reading that other people like to call “ruining it”, so that may color my viewpoint. But when I flip through my copy of Paradise Lost and see all the notes I wrote in the margins, all the words I circled and connected to other words, I can actually reexperiece not just the work, but what it was like to read the work that particular time. I can look back and see how I was thinking then, what examples I was bringing to bear, what issues were on my mind. Whenever I read Paradise Lost in earnest a second time (I reread sections alot) I will get another copy. Then, 20 years from now I can compare the notations in the two (and maybe others) and have a more telling “snapshot” of myself at a particular age than any photograph.
I love the way works that I have really taken apart and examined look when I get done with them–my “Benito Cerino”, for example, has every paragraph numbered, to corrospond with a lost notebook, and cf.s throughout. It’s like looking back on a tall mountain and seeing the flag you planted waving on the top–it say “I was here, I mastered this” in a profound way.
Marginalia by really famous people is a treasure trove for biographers, and while I don’t really think I will have many of those, my grandchildren might enjoy seeing what I did to my favorite books.
Also, I am simply not smart enough to remember all I want to say, all the little connections I am starting ot see in a Great Book without notation. Sure, my bestsellers, my romance novels,those sorts of things I just tear through and don’t write in. But when I am reading a complex work, I can’t do the author justice without notation.
As far as the condidtion of my books: that depends on the type. Cheap paperbacks I abuse terribly, I try and keep the reference section together and in good condition, mostly so that I can find things when I need it, though all my style guides are worn to hell. I throw away dust jackets as soon as a purchase a book, since they tend to start looking ratty with even casual usage, and the book looks better bare than with a ratty dust jacket.