The process of elimination

The best way to tackle a collection of post-1900 printed books is to eliminate books that will not be of value.  You will find that you will eliminate most. 

Remove any book that:

1.  Does not have a dust-jacket.  A dust-jacket is a paper cover which publisher's place over hardcover books, much like the books you see today.  Any book printed after 1900 will have been issued with a paper dust-jacket with only very few exceptions such as finely bound or limited editions, or some books printed between 1900 to about 1910.  But 99% of the time, no jacket = no value.  That 1% is reserved for books which may not have been issued with a jacket, or books that have some other important aspect such as the author's signature.

2:  Is a Paper-back.  There are a few exceptions, but 99% of the time when you see a paper-back, it is a reprint and is not going to be of value.

3:  Is a text-book, self-help book, history book, owner's manual, dictionary, encyclopedia, magazine (including National Geographic, etc), or recent fiction by authors such as James Patterson and the like.

4:  Is ex-library (with markings, etc.), is water-stained, is drawn in by children, or has similar obvious defects in condition.  Remember, condition is very important, and collectors expect modern printed books to be in excellent condition.

5:  Is a multi-volume set of The Works of ________(fill in the blank).  "Author sets," as we refer to them, were commonly printed in the early 1900s, often in "limited editions" that were anything but.  It could be the Works of Twain, Thackery, Dickens or other such authors.  These are of little value unless they are finely bound in leather/gilt, or are signed editions.  The usual 'limited edition' of an author set is bound in cloth and is unsigned. 

6:  Any book that is volume 1 out of 3, or volumes 1-5 out of 10, or any partial or incomplete set.  If a book is incomplete, then the value is entirely lost with modern books.  An incomplete set is much the same in this respect.

Once those steps are taken, your collection should be significantly smaller, and most modern collections would be eliminated entirely just based upon those criteria.  From here, we move on to other criteria which may require a little more time.  So, of the books you have left, remove:

7:  Any work of fiction that is not either a first printing or signed by the author.  Reprints, even if only the 2nd printing, are typically of little value unless they have some special attribute such as being signed by the author. 

8:  Any other book that is not a first edition, excluding limited or special editions.

At this point, if you still have any books left, identifying valuable books becomes more difficult without some expertise.  But at least the number of books you will be working with should be greatly reduced.  Now, you may begin to look at the books with an eye not for exclusion but for inclusion in your list of possible valuable books.  Below, you will find a list of the types of books that will tend to be valuable:

Pay attention to any book which:

1:  Was written by an author you recognize as important or popular.  Examples would be Hemingway, Fitzgerald, Faulkner, Jack London, Nabokov, Salinger, and similar.  If you've not heard of the author, then the odds are less that the book will have value.

2:  Is a title which you recognize as important or popular.  Examples could include Gone With the Wind, The Catcher in the Rye, Call of the Wild, Interview With a Vampire, The Old Man and the Sea, Lolita, The Cat in the Hat, etc.  If you've never heard of the author or the title, then the odds are less that the book will have value.  Keep in mind that some of this is relative.  If you are 20 years old, there may be numerous authors and titles you are not familiar with.

3:  Is an illustrated, signed and limited edition.  Some of the most valuable books printed during the 20th century are these types of books. In the earlier part of the 1900s, there were quite a few books beautifully illustrated by artists such as Rackham, Dulac, Pogany and others.  These books were typically first printed in a limited edition, and those editions are often nicely bound and signed by the artist.  However, keep in mind that reprints that followed are nice but typically not of much value.  Another example would be a limited edition Picasso book which contains (for example) one or two original lithographs or perhaps is signed by Picasso.  These are things to look for, and such factors should generally fit into the realm of obvious.  In other words, when you see them, you'll probably know you're holding something special.

SUMMARY

By no means are the above criteria exhaustive, but by and large, most valuable books printed after 1900 tend to be important or renowned works of fiction by major 20th century authors, or finely illustrated and limited editions.  Certainly there are exceptions.  For example, a first edition of Einstein's work on Relativity clearly is not fiction, but it is quite valuable.  The categories mentioned above are simply a very general  guide to assist you in creating a list to send to us without spending large amounts of time listing books which are not going to be of value.   

The typical 20th century collection we evaluate will often contain no books of significant value at all.  When valuable modern books are found, they tend to be found within the library of a serious collector.  Typically, collections of modern books are more of what we would call "accumulations" or "hoards" rather than collections.  Perhaps your great-grandmother passed them down to your grandmother (who added to it), then to your mother (who added to it), then to you, etc.  Unless one of them was a serious book collector (not a hoarder or simply an avid reader), then the books are not likely to be valuable.  If you bought a box of used 20th c. books for $5 at a garage sale, then you probably paid too much.

When you contact us regarding modern books, it is always important to list details of particular importance.  So, when making a list, include:  Author, Title, Publisher, Printing Year, Condition notes, whether or not the book is a first edition, note if the book is signed by the author or possesses some other important attribute, and always note the presence or absence of the dust-jacket.  Without this information, it is impossible for us to evaluate the books.  If you only have a few books, you can always opt just to send photos.  In that case, we will need to see the entire jacket, the hardcovers, the title-page, the copyright page, and the price on the jacket.