The best series of books on world coins are the Krause catalogues, called the "Standard Catalog of World Coins". The catalogue is divided up into volumes by century, and each volume is quite large (the "size of a phone book"). The 20th and 21st century volumes are updated every year, the earlier centuries are updated every few years. They only go back to the year 1601.
Krause Publications (the people that print the catalogues) also maintain an online database, at http://www.numismaster.com - accessing the database is free for identification purposes (click on "find my coin") but if you want mintage figures and catalogue prices, you have to pay a subscription.
Another good site is http://www.worldcoingallery.com - this is a private collector's database, comprising mainly circulation coins and mainly coins from the mid-1800's on. It's also got some good "Identify your coin" tips and help pages.