Converting a new, large perfect bound paperback to a durable hardback I bought a book which is paperback and very large: 697 A4 pages. It appears to be what is called perfect bound, that is, where the spine is adhered directly to the back of the pages. At a minimum, I am going to put a hard cover onto it to protect the corners which I know will otherwise inevitably be damaged in the normal course of use. I am not anticipating excessively heavy use, but I'm definitely going to use the book and at 700 pages there's a lot to use.

In addition to the cover, I am worried about the binding. I am wondering:


If I do a good job putting hard covers on it, but leave the current binding intact, how much should I be worried that it will break down, considering the size and weight of the book, and the nature of perfect binding? Is there anything I can inspect to get a sense of how good the binding is?
If the binding is glued, is it even possible to sew it instead? Would there even be signatures? Or is there some other way to solidify it?


That looks like a lot of different questions, but they are just different angles on this question: If I want this large book to last, should I rework the binding in addition to the cover?
This sounds like a much better candidate for honing your book-repair/book-binding skills.  If your goal is solely to increase the book's durability, then you have several options available...

If the book is recently published, it may be available as an e-book.  Author's will sometimes offer discounted e-book versions of their books to owners of physically printed copies.  E-books are the ultimate in durability as even if your e-book-reader gets destroyed, as a registered owner, you can usually just download a new copy into your new reader.

Alternatively, you could use a blow dryer to separate the pages of your perfectly bound copy, then put them in sheet protectors and mount them in a three ring binder.  I did that to some of my college textbooks thirty years ago and they are still perfectly readable today.

For a real binding solution, it is pretty simple to add cardboard reinforcements to the currently soft covers and spine.  Here is a very complete tutorial on that process.

Beyond that level, you will need to separate the pages as in the 3-ring binder approach, but once you have done that, a number of diy book binding techniques become available.  There is a youtube channel called Sea Lemon which goes over quite a few string binding techniques.