1,pen bag can use with any books ,if you want to use with your books ,firstly print ours specialization CODE on the book. 1,pen bag can use with any books ,if you want to use with your books ,firstly print ours specialization CODE on the book. secondly recording the book by wav format . 2,we already have many kinds of the children books with fun content ,good for the child learn languagers.3. the ...