There are many excellent references works on VAMs. The hobby is information driven and these references help collectors understand and enjoy collecting.
The Comprehensive Catalog and Encyclopedia of Morgan & Peace Dollars by Leroy C. Van Allen and A. George Mallis. Affectionately known as "the big VAM book" by collectors, this is currently in its fourth edition. First published in 1971, it was updated and reprinted in 1998. It contains a detailed listing of all known (at the time) die varieties listed date-by-date and is loaded with pictures. At more than 500 pages, it contains a wealth of mainstream information dealing with the history of Morgan dollars, grading, counterfeit detection, photography instruction and more. Leroy Van Allen has also put out supplements and detailed attribution guides since this work was published.
The Top 100 Morgan Dollar Varieties by Michael S. Fey Ph.D. and Jeff Oxman. This guide lists popular die varieties with descriptions and detailed pictures. It offers rarity information as well as suggested values. You can purchase the latest guide, the 3rd edition, [Available from Dr. Fey's web site, RCI Inc]
1878 Morgan Dollar 8-TF Attribution Guide, 3rd edition. A guide to attributing the 8 tail-feather Morgans. It includes a system for determining the VAM number. It includes rarity and value information as well. By Jeff Oxman and Less Hartnett with photos by Bill Fivaz, [directly from Jeff Oxman's web site, VAMlink.com]
1878-S Morgan Dollar Attribution Guide by Leroy Van Allen and Craig Lickenbrock, July 2006, 100 page bound copies with 377 photos, $19.95 + $3 P_H. Direct orders to Leroy Van Allen P.O. Box 196 Sidney, OH 45365.
The Official Guide to the Top 50 Peace Dollar Varieties by Jeff Oxman & Dr. David Close, Photos by Bill Fivaz and Dr. David Close. A picture-filled reference detailing the most desirable Peace dollar varieties. [Available from Dr. Fey's web site, RCI Inc]
Elite Clashed Morgan Dollars written by Mark Kimpton with photos by Leroy C. Van Allen. The 147 page book offer hundreds of photographs, descriptions, rarity estimates and values for many clashed Morgan Dollars. [Available from Dr. Fey's web site, RCI Inc.]
1879s Reverse of 1878 Morgan Dollar Book by David T. Wang. A 52 page book that attributes 15 varieties of this top 100 coin with hundreds of reference pictures have been released. The Results of the collaborative research by Mr Calvin Cherry, Mr. William Eubanks, Dr Mike Fey, Mr Leroy Van Allen, and the author David Wang is presented to the Numismatic Community. [Available from Dr. Fey's web site, RCI Inc.]
Fun With 1921, Denver Morgan Dollars with Die Breaks, Die Gouges and Filled Dies, by Rob Joyce.
A detailed study of the die varieties produced at the Denver mint in 1921. Currently out of print. VAMworld information is more current.
The SSDC 7/8 TF Attribution Guide. Identification of 7 over 8 tail-feather Morgans. It includes attributions for all 7/8TF and B1 reverse varieties. By Less Hartnett and Jeff Oxman with photos by Bill Fivaz.
SSDC Official Guide to the Hot 50 Morgan Dollar Varieties. An attribution guide for additional varieties beyond the Top 100 list. By Jeff Oxman with Photos by Bill Fivaz. Currently out of print. (Copies appeared at the Baltimore show, Nov 2008. Available soon?)
Guide Book of Peace Dollars, by Roger W. Burdette with Barry Lovvorn. As the 13th entry in Whitman's Bowers Series of numismatic references. It covers every date and mintmark of America's last 90% silver dollar, which began as a commemorative of peace after the tribulations of World War One. The book also studies the mysterious 1964-D Peace Dollar, as well as proofs, patterns, trial pieces, errors and misstrikes, countermarks, die varieties, and famous collections. Full Color, Softcover, 288 Pages, Fully Indexed. [Available from Whitman publishing]
Elite 30 Peace, Published on Feb 4, 2013 by Dr. David Close, Numismatic author and researcher.
A new book featuring 30 of the most significant Peace dollar varieties has been written. See examples of each of these new findings and what diagnostics to look for in this specialized area of numismatics. [Avaliable from VamsAndMore]
Morgan Dollar Overdates, Over Mint Marks, Misplaced Dates, and Clashed E Reverses, by Kevin Flynn, 1998, 6*9, 120 pages, 500 photos. A detailed analysis of these varieties, including many Morgan Dollar misplaced dates that were not previously shown at this time. The book also refutes the 1882-O/S varieties as simply a progression of die cracks and refutes some of the 1880 varieties that had been classified as overdates. Available from Flynn's web site, www.kevinjflynn.com
Off-Center and Multi-Denominational Clashed Dies, by Kevin Flynn, 8-1/2*11, 112 pages. A complete analysis of the cause and effect of die clashing and presents an in-depth study of many of the Morgan Dollars that have been classified as denticle impressions.