If you have an account with SubetaLodge, SL has a feature which allows you to make checklists for collections such as pet's books.

Go to Lists > Mass Add/Update on the top navigation bar

Then go to the correct page(s) showing the collection and copy the source code for the page, and you will have to do this for however many pages of books your pet has read.

You can check books your pet has ready by going to Personal > Pets > Books read (on the drop down next to your pet)

If you have any further questions, please make sure to press the little megaphone icon on the top right of each post to alert the user you are replying to.

Also moving this to Entertainment > Internet, as this is a question about a Subeta Fansite.

Thank you :)