The Firebird Book (Second Edition) is now available as a print on demand book (at createspace) in three parts,

Volume 1: `Firebird Fundamentals
https://www.createspace.com/4203352

Volume 2: `Developing with Firebird Data
https://www.createspace.com/4206843

Volume 3: `Administering Firebird Servers and Databases
https://www.createspace.com/4206991

Regards
Paul