Bookworms,
Without getting into the Dewey Decimal system libraries use, there are several
ways to organize those books...basically in ways that make sense to the user.
1.  Sort by categories & arrange alphabetically - whatever makes sense to you
     a) Preservation Issues
     b) Restoration Manuals
         l - stone
         2- wood
         3- metal    etc
     c) White papers, history
     b) Historic sites    for example

2.  Sort each category alphabetically by title

3.  Use the same arrangement for those placed in the file cabinet vs the
shelves.

4.  Alternative:  All books (and research materials) are filed alphabetically
no matter what the subject.  I find this awkward, however, since it means
checking the whole library to find the restoration procedures books amongst
history of the state or geological conditions of 1672 Wallingford, CT.

5.  Keep a stack of those manila dividers that say "OUT" handy and USE THEM.
     Mark on the divider which book is "out".  When your stack of "to be
shelved" gets too high - walk down the aisle, pull the "out" divider & see
what goes there.

     Any sheet of stiff paper will do as well - even if you don't write the
title (afterall, you are filing alphabetically) you will be less inclined to
stick the book back any ol' place.

6.  You may want to mark the spine of the book (in a non-intrusive way of
course!)
     Best would be which category you assigned the book to.  It alleviates
figuring out later which spot on the shelf to head to.

     Ways to indicate categories: (afterall, you want quick refiling-and
research)
      a) by color:   Label your shelf section with the name of the category
and a one of those color sticker dots, (or grab your paint brush).
Make sure the label is easily moved as your collection grows and need a
different space.
Label your book with the same color.  If you don't want to put a color sticker
(which may fall off anyway) on the spine....slip in a bookmark of the same
color inside the cover.  If you subcategory your collection (for instance
Restoration Methods / stonemasonry) use your main category color for
Restoration Methods and then another for stonemasonry. Eg. Dark Green =
Restoration Methods; Pastel Green for subcategory stonemasonry.
Don't forget to label & color code the file folders as well.

      b)  by number or symbol:  Label shelves, file drawers and folders the
same as with colors.

The more color coding, numbering, symbols you use...the more tightly the
system is organized...but if you go through that much trouble, you defeat the
purpose of your original question of ...small library...easy organization.

Summary: Sort by categories you find useful - don't go crazy, keep it simple.
                Assign a color...mark the location, mark the book or folder.
                Mark spot when its removed.....replace to that spot when you
are done.

Lastly:  Computerize your library.
            Microsoft Access has a preformatted Book List database.  I'm sure
others do as well or create your own.  Its an efficient way (on a form) to
input each title, author, category, notes etc of each book you own.  Just add
to the database whenever you get a new item.
You can print out the whole list to keep handy and the database will
automatically sort it according to alpha title, author, category...whatever
works for your purpose at the time.

I would suggest the "big category sort first" then go on from there. Once in
place, you can do the database shelf by shelf as time permits. You can alpha
later, too, as long as the book knows where's its general location is.

Hopes this helps,

Candy Brashears
The Guild of Fine Craftsmen & Artisans
Woodbridge-CT