As one can see that the books on left do not remain straight after few days. They become inclined. This affects the bottom corner of book, it gets folded with a large radius.
2 Answers
The normal solution is to use bookends:
(random image picked from a 'bookends' image search)
You can buy these, but you can also build them yourself. One option is to get a few pieces of wood in A4 size and attach them to the wall (or to your existing shelf on the left) vertically, then insert the books and binders between them.
Put all weak books in hard cover book. Another way to prevent is put all Books horizentaly such as the name of books is show to u. Put a hiegh wight at the end of book. Its helps not to slip books. Or use a bookends as mention above.