My favorite book that is out on grading coins is the old PCGS book, "Official Guide to Coin Grading and
Counterfeit Detection" I preferred the first edition myself in the quality of printing, but there is a 2nd edition that came out a few years later. I still have the 1st edition in my library and the price is now affordable at around $12-20 for a lightly used copy online, for awhile they were really hard to find and selling for close to $75 or $100 each not 5 years ago. A pretty darn good book over all. I sold off my copies of the
ANA Grading standards in color, and older Jim Ruddy Photograde (circulated coins) books except for a really early Photograde book Dave Bowers gave me as a gift many years ago, though I really never refer to it preferring the online photograde website at PCGS as mentioned previously.

The Halperin book mentioned by MisterT is also a good book for learning high wear points on
US coins, Jim did a great job in using color overlays on coin photos to show spots to look for.
Other good books to consider are used or search online at
ebay, abebooks,
Amazon, etc. Most of the following can be found used for under $15 each with some patience and searching (except the EAC book, that is expensive and advanced).
Grading Coins by Photographs, Q. David Bowers
Official
ANA Grading Standards for
United States coins, Ken Bressett
Guide for Grading Coins of Canada
Grading Guide for Early American Coppers
The best book for early copper colonial and half/large cents out there not a cheap book, nor will you likely find a copy for under $50.
No book or set of photographs can completely replace the experience that comes with viewing lots and lots of coins. Thus, to start to develop coin grading skills, one should balance a review of grading guides and books with the study of as many coins as possible. One should compare coins of different grades, identify the differences between the coins and relate those differences back to the components of the grade described in the coin grading guide. The very best thing I ever did to get as good at grading as I am (I think pretty good) was to attend the
ANA Summer Seminar I've taken 3 grading courses basic and advanced twice, as well as
Counterfeit Detection among four or five other courses over the past few decades.
No better learning area to start from, though not cheap, my first time was free as a young numismatist through a scholarship (which was not hard at all to qualify for and receive). Today the cost is substantial at well over $1000 and travel to Colorado Springs for a week, but worth so much more from what you get out of it.
Also going to view many, many auction lots at major auction houses Heritage, Stack's, Kagin's Goldberg's etc. and view at big coin shows, help more than you might think. Look at thousands and tens of thousands of coins, you will learn all sorts of things about them individually (date/mint mark) and as a series, there is no substitute from seeing and holding the coins in hand as well as having a qualified mentor to help guide you.
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440