>I'm new to Firebird, I like it very much and I want to learn the maximum as
>soon as possible.

>My question is: whose are the last books or articles or docs about Firebird
>and where I can find them?

Get hold of Helen Borrie's "The Firebird Book". Available from www.ibphoenix.com

>Into the Firebird's site there are several docs but most of them are
>out-dated, I prefer new reading material, material that cover versions 2.1,
>2.5, 3.0. I don't like to read about version 1.5 or prior because seems too
>old.

Don't worry about that. If the info hasn't changed since FB 1.0, then the docs won't be updated, and apply to all versions.
My main reference was actually the interbase 6 getting started docs for a very long time, when I first started using Firebird 1.0 and 1.5. The information doesn't go out of date very quickly.