I've placed the first book of a Firebird 2.0 manual on-line: http://www.janus-software.com/fbmanual/
This book is about the stored procedure and trigger language "PSQL" and consists of about 100 web pages. I would expect that all 8 planned books will be online before the end of the year. The on-line manual is user editable, in the sense that users can post extra information, examples and corrections -- in the style of the on- line PHP manual. All feedback is welcome.