Are you considering starting a D&D Group in your Library but do not want to start buying the required gear until you are sure that you know what you are doing?
Well good news!
The Wizards who live on the Coast have made the Basic Rules for Dungeons & Dragons free to download as a PDF (over 100 pages, in fact) that covers the core of the game. It runs from levels 1 to 20 and covers the cleric, fighter, rogue, and wizard, presenting what we view as the essential subclass for each. It also provides the dwarf, elf, halfling, and human as race options; in addition, the rules contain 120 spells, 5 backgrounds, and character sheets.
USING THESE RULES
The Basic Rules document is divided into three parts.
Part 1 is about creating a character, providing the rules and guidance you need to make the character you’ll play in the game. It includes information on the various races, classes, backgrounds, equipment, and other customization options that you can choose from. Many of the rules in part 1 rely on material in parts 2 and 3.
Part 2 details the rules of how to play the game, beyond the basics described in this introduction. That part covers the kinds of die rolls you make to determine success or failure at the tasks your character attempts, and describes the three broad categories of activity in the game: exploration, interaction, and combat.
Part 3 is all about magic. It covers the nature of magic in the worlds of D&D, the rules for spellcasting, and a selection of typical spells available to magic-using characters (and monsters) in the game.
Grab them here: http://dnd.wizards.com/articles/features/basicrules