DS is not quite 3.5 and loves books, loves to "read" them, loves to be read to, goes to the library frequently, goes to the bookstore frequently, is allowed to pick out books as gifts with grandma frequently (generally junk) on these visits, and recieves new books from us as well, usually from my stack in the closet for whenever I feel the need.
We like books.
Recently he started to tear them which is really distressing. He never did this when young, although DD 1.5 does it sometimes. It seems random, is often of books he really likes, and sometimes bad enough to ruin them. DH is especially upset by it but also points out that he is also into cutting things right now and it seems to be going through an art "leap" with drawing and recently made a book with his nanny. We aren't sure if those are related.
He seems to feel bad after the fact, readily apologizes, but it keeps happening. Last night it was his new pirate dinosaur book that he has loved, read a ton of times, and inspired art all weekend long. We went to read it before bed and 4-5 pages are missing and he couldn't find them.
What are natural consequences here? We aren't replacing books he has ruined although I am repairing them to the extent possible. We decided last night that we wouldn't be allowing any new books for two weeks, until we have a period when books are again treated with respect. Any new books that accidentally arrive can be put away for another time.
We have lots of books here and I LOVE books. What we do is keep books generally public.
The bookshelf/books are in the middle of our living area. So book use is in the middle of life. We'd hear any page tearing. When DS was younger he did tear books when in bed, so he was never allowed library books or paper books (but some board books) in bed. We talked about how he needed to learn to be gentle with books and not tear them. Now DS is 3 and he does get to have books in bed again. I think we may have also let him tear construction paper or something when he seemed to really like tearing. But no books.
I don't know if it is over-guilting or what, but special books that he ripped up I'd take a while to repair and if they were beyond hope and he wanted them again I'd remind him - Oh, sorry, we can't read that one anymore because you were still learning you need to be gentle with books and it was ruined. Now you know how to be gentle with books, don't you? :)
I don't know how you have things set up in your house, but if they aren't in a public space you can try changing that.
I should add too that my DS is about the same age as your DS now and if he just started tearing books out of the blue I'd be pretty upset. I do think that he is doing some imitating of your DD for attention, perhaps? My older DD will sometimes try out negative behaviors that she was well beyond just to see how we would treat that behavior from her compared to her brother.