Where are the docs?
If you're looking for offline books, we can highly recommend The Firebird Book by Helen Borrie, which is the ultimate resource for any Firebird developer.
If you're looking for complete docs in electronic form, you should gather the following:
- Interbase 6.0 manuals
- Firebird 1.0 release notes
- Firebird 1.5 release notes
- Firebird 2.x release notes
Basically, IB6 manuals contain 90% of everything you need, and release notes add the features (and bug fixes) made to the Firebird since IB6.
Most important PDF in IB6 docs is The Language Reference, so make sure you have that one at hand. You can find download links for all documentation on this page:
Also, make sure you take a look in 'doc' subdirectory of your Firebird installation. It contains a lot of useful information.