From Freedom to Slavery, by Gerry Spence (Randy Weaver's defense attorney) -- this is one of the best introductions to what happened at Ruby ridge

Excellent background article from the Wall Street Journal

Some other good sources on information on what happened a Ruby Ridge:

Wayne LaPierre's Guns, Crimes, and Freedom, pages 179-190 of the hardcover edition is the best, concise overview available. It's also available in paperback.

For thorough coverage of the story, read Alan W. Bock's Ambush at Ruby Ridge, all 332 pages thereof.

Jess Walter's Every Knee Shall Bow is even more detailed (464 pages).