There are some books for which the 'full monty' of repair is either not required, not recommended, or not affordable. The Archiving process 'CCB' (my bindery shorthand) option is very useful in these situations.
For example, this book is made of precarious materials. For this book, the more you touch it, even to repair, the more secrets it gives up; the more you do, the more it seems there is to do. It's owners are happy to let it sleep, and frankly do not wish to spend more than absolutely necessary to slow it's demise, so a working repair to frequently open and close the book wasn't required, and to do light repairs may well have offered false security for anyone handling it; best to...
Clean, Consolidate and Box (with a mylar cover sleeve to keep everything in it's place)
Clean - mechanically (non-aqueous treatments only) with various instruments and materials to remove as much dust, smoke, frass (dead microscopic things), stain, old tapes and adhesives, stickers, marks, botched repair attempts, general mess and occasionally mold.
Consolidate - using various substances to re-size paper, recover mangled parts, strengthen cloth, or treat failing leather. Sometimes light Japanese tissue is used with very thin paste to keep some bits together temporarily until future work can repair it completely. Also inclusions or detached parts are cleaned and enclosed in inert mylar to keep with the book, but not inside or up against it.
Box - construct a custom enclosure from specialist archival double-wall board that will physically protect the book in transit and storage, and limit and slow down the rate of environmental changes - heat, light and humidity.
Here is another example of the Archiving process offering a practical option for a book. This one had brittle, cracking adhesive on the spine that was damaging the pages every time it was handled. The book has had an accident in the past with a substance that has stained and shifted it's colour, and left residues all over the place - likely petroleum-based. The spine is off and very delicate. It also doesn't help that upon cleaning, it was revealed that whoever sewed the book originally left one cord unsewn in the middle and just filled that groove in the spine with glue. :(
This book will likely be fully repaired in the future, but for now, CCB is a very gentle and helpful first step.
Sometimes, archiving is a preventative measure for a book that is not in need of repair at all, and the owner would like to keep it that way.
For a particularly valuable book or first edition, it is the only option I offer.
Archiving is the least intervention, and so least invasive help a book can get in my bindery. It is also the most cost-effective in the short term, especially if you have a stack of candidates for repair. Currently, I am Archiving a collection of 30 or so books - an inheritance - with just a few getting the full treatment, and the others waiting to see how they are received by my clients grandchildren.
If aesthetics are important, sometimes the practical conservation board is replaced with a more pleasing decorative but still archival box. This is also a great choice for paperbacks that you wish to keep and love, but that will show you no love back for costly interventions.
Uuuurrgh - paperbacks. That is a story for another day.