IU doesn't have every book. If you are not finding what you need in IUCAT, then search WorldCat, which contains books from libraries all over the country. If you find a good book, you can request it via InterLibrary Loan.
A call number is the unique number given to each book in the library. Call numbers are like addresses, they tell you where a book will be located in the library.
If you understand how to read a call number, it will be a lot easier for you to find books in the library.
This library uses LC call numbers (LC stands for Library of Congress), which use a combination of letters and numbers. The same exact call number can be written 2 different ways:
A call number that you find in IUCAT (the online library catalog) will look like this: CT105 .K55 1981
And that same call number will look like this on the spine of the book:
CT
105
.K55
1981
So, here's how you read a call number on the spine of a book:
And here is how this book would be placed on the shelf:
CT 104 .P281 1930 | CT 104 .P7 1830 | CT 105 .H866 1995 | CT 105 .K55 1981 | D 105 .H43 1992 |