Digging into WordPress, by Chris Coyier and Jeff Starr, is available in its third edition today as a PDF download only for $27.

The new edition includes an updated design and new information on WordPress 3.0. Printed versions, according to Starr, may be available in September or October.

Coyier and Starr began publishing Digging into WordPress via their website DigWP.com in 2009. You can follow Coyier on Twitter @chriscoyier and Starr @perishable.