Databooks gives vital statistics like hight, weight, birth date but NOT age. They also give Zanpakuto names and release commands, indeed Komamura's release command is only given in the MASKED Databook. They Databooks also provided additional information on events that have taken place, include additional information on places of interest like Karakura Town, Soul Society etc, etc.
In previous Databooks, Kubo has also included never before seen short-stories in Databooks. However, the newest Databook, the MASKED, doesn't have any new stories.