Here is an answer from our head of collections care, Sarah Stauderman:

Your grandfather’s journal reminds me of the many scientific field notebooks that we have at the Smithsonian Archives, not to mention the diaries and accounting ledgers that form so much of our collections.  It is wonderful that you still have these original documents.  There are just a few simple ideas that will help preserve them for your family.

Considerable amount of scientific research has gone into studying what are the factors of deterioration.  By far and away the two factors that will preserve or destroy these books are: temperature/humidity (environment) and handling. One way that we manage both of these factors is by placing books into handling containers as described by our colleagues at the Northeast Document Conservation Center http://www.nedcc.org/free-resources/preservation-leaflets/4.-storage-and-handling/4.5-protecting-books-with-custom-fitted-boxes

The boxes provide protection against fluctuations in temperature and relative humidity.  In Arizona, where you live, I imagine that the books are never exposed to high relative humidity; in Baltimore, much more care must be taken to ensure that the books are not exposed to a relative humidity more than 65%, otherwise mold can grow. We advise not to put important items into a basement or attic. The boxes also provide some protection against rough handling; we’ve noticed that when items are in neat boxes that people tend to treat them better.

One way to ensure that future generations will be able to enjoy the books without handling them is to digitize the book using a camera copy-stand configuration.  While this can be technically challenging, there are many resources on digitizing books, including this blog post on our site: http://siarchives.si.edu/digitizing-photo-albums-and-historic-books-submitted-email

There are many other features of the books in your possession, such as the paper type, inks used, binding (which you  note is probably a standard office-type binding), and so forth, and all of these interact together to be a unique document that needs attention.  Remember to handle the book with care; clean hands, patient turning of the leaves, and observing the changes that will happen over time. Many journals of this time period are relatively strong and do not deteriorate quickly; the only other feature that will signal quick deterioration is acidic paper.  If you notice that the paper is embrittled, brown, crumbles easily, then you will need to have the book looked at by a book or paper conservator.  Here is a guide for finding conservators: http://www.conservation-us.org/about-conservation/find-a-conservator

I wish you all the best with safekeeping your grandfather’s ledger.  Thanks for being in touch with us.

Your concern seems not to lose those accounting books.Like various elements can damage a book, and it doesn’t take much. According to Cornell University, as soon as a book is exposed to excessive moisture, heat or direct sunlight the book’s structure may be compromised to the point where it may potentially become permanently damaged. The rule of thumb is to store your book(s) in a place with lower humidity fluctuations and a relatively normal temperature range (no attics or basements!). When it comes to preserving old books, it’s important that you try and maintain these conditions at all times. Books can also be affected if the environment changes seasonally. If you have an in-home library, keep the temperature between 65 and 72 degrees Fahrenheit. The air should also have a humidity level of between 30 and 50 percent, as Cornell noted. If you’re worried about your home’s conditions, don’t fret, as there are plenty of ways you can control these elements. If your home is prone to excess humidity, consider getting a dehumidifier that will remove the extra moisture. You may also want to keep your important or valuable books in a closet or darkened unused room as light—especially direct sunlight from a window—can cause ink to fade and leather or fabric bindings to age more quickly.

Your job should keep your books in a place where conditions do not change all that drastically. This means avoiding storing books in basements, which are vulnerable to floods (naturally occurring or via leaky water heaters), or attics (with their potentially leaky roofs). Both basements and attics also typically experience extreme heat and humidity fluctuations. Instead, consider placing your important or rare books in a dark, cool closet. Regardless of where you store them, be sure to dust regularly to prevent mold spores from building up and eventually growing on the books’ pages. If the books are placed on a shelf (always out of direct sunlight!), try to keep books with others of the same size. That way the pressure is equalized and a smaller book won’t “indent” on a larger book next to it. You should also make sure your books are stored upright, not slanted or on top of one another. Use heavy bookends to help keep them in place.