If the cover has creased, the layers of the paper will have separated and the fibres pulled out of alignment. The crease is then bulkier than the rest of the cover and stretched on the side it bends away from.
As you cannot push the fibres back into their former alignment, this is a technique I have used to get the cover to lie flat. Note, don't do this ...
I also travel a lot with paperback books in a bag, and I've managed not to damage them too much by considering the problem as a geometrical/physical one, analysing the shapes and forces involved.
A paperback book is essentially a cuboid, with two faces that can peel away from the rest and keep peeling away in pages until you reach the middle:
As long as ...
I don't believe dustjackets protect a book to a significant degree. But I am in favour of keeping them with the book.
Dustjackets are often prettier than the book.
The flaps of a dustjacket can be used as bookmarks (unless the book is very big).
The dustjacket can be removed while the book is being read and left on the bookshelf as a marker of where it ...
Friction acts on the book regardless of whether it's fixed or not. If a bag doesn't have a special compartment for books of laptops, it may be beneficial to acquire a book cover. It can be plastic, paper, or even textile, depending only on one's choice
Plastic covers (also called wraps) seem to be available online (e.g. I took the picture above from here)...
I use a tupperware/kliklock container, but I if I am short of space, putting the book in with a laptop in its case keeps it flat (not instead of a laotop). Also if you put a clipboard into the back pack it forms a rigid and flat central divider that is not deformed when you strap it to your back which is the main issue.
Covering a book with a flexible ...
The dust jacket is more delicate than the stiff covers of a hardcover book, so it does not really need to be around the book while you're reading it. In fact, that is a good argument for temporarily removing the book jacket while you're reading the book. As Biblio.com points out (emphasis added),
The dust jacket is both the most decorative part of a book, ...
Part of me takes a not altogether perverse pride in the battered appearance of many of my books; but when I want to protect one from battery in my bookbag, I favor an appropriately sized mailing envelope lined with bubble wrap, available at office supply stores and sometimes even supermarkets in my country (USA).
According to NLR in Australia, there are various ways to [get rid of mould in books]:
freeze drying with anti-microbial treatments,
vinegar / alcohol solutions
The page contains a video showing someone using a HEPA vacuum cleaner. The cost of this service is not mentioned on the NLR ...