There are a number of US paper money reference books and price guides available.  Here are a few of my recommendations.

Paper Money of the United States
by Arthur L. and Ira S. Friedberg

Get this book if...

You collect multiple currency types, use the Friedberg numbering system, or enjoy looking at old currency.

Buy It on Amazon

Current Version:
20th Edition

Previous Versions:
19th Edition
18th Edition

Summary

This is one of the most popular US paper money references available.  Written by Arthur and Ira Friedberg, it is the source of the Friedberg numbering system.  This alone makes this book worth owning for many collectors.Paper Money of the United States covers a wide array of currency with images and values at various conditions for each:

  • Small Size (1928-present)
  • Large Size
  • Fractional Currency
  • Encased Postage
  • Colonial/Continental Currency
  • Confederate Notes
  • Error Notes
  • National Bank Charters
  • and others

Standard Guide to Small-Size U.S. Paper Money (1928 To Date)
By John Schwart and Scott Lindquist

Get this book if...

You only collect modern U.S. paper money (1928-present) and/or want ALL the details about Small Size notes.

Buy It on Amazon

Current Version:
10th Edition

Previous Versions:
9th Edition
8th Edition

Summary

As the title indicates, this book focuses solely on Small Size notes.  It seems to contain a slight bit more information about Small Size notes than Paper Money of the United States.The Standard Guide breaks down most note values by FRB (or prefix) and block letter/suffix, whereas Paper Money of the United States does not.  The Standard Guide also provides low/high observed serial numbers where possible.  Both Paper Money of the United States and the Standard Guide work equally fine for looking up note values.

The Standard Guide excels in organization for collectors who want to research the gritty details of Small Size note variations - mules, light vs dark seals, wide vs narrow plates, narrow vs wide seals, etc.  For example, the Standard Guide has a section for:

  • $10 1934 Light Green Seal
  • $10 1934 Dark Green Seal
  • $10 1934 Mule Dark Green Seal

And another example:

  • $5 1934C Mule Green Seal
  • $5 1934C Green Seal - Wide Face
  • $5 1934C  Green Seal - Narrow Face

Paper Money of the United States goes as far to differentiate to mules and between light and dark seals.