from the Foreword:
This “Complete”-manual has been created to give the old AD&D a polish. It is by itself not very abstract or complicated or holds tons of overwhelming new material. But it is a compilation of nearly almost all existing nonweapon proficiencies of the second edition of AD&D, which were splitted in many different handbooks. Because of this you will be able to spare collection of all books (and carrying) and still you have all proficiencies with you at once, saving a lot of time. Part of this complete manual are:
Players Handbook, AD&D 2nd edition
The Complete Fighter’s Handbook
The Complete Paladin’s Handbook
The Complete Ranger’s Handbook
The Complete Priest Handbook
The Complete Druid’s Handbook
The Complete Wizard’s Handbook
The Complete Psionics Handbook
The Complete Thief’s Handbook
The Complete Bard’s Handbook
The Complete Barbarian’s Handbook
Elves, Dwarves, Gnomas & Halflings, Humanoids Handbooks
DMS Option: High Level Campaign
DMS Option: Combat & Tactics
Players Option Spells & Magic
Players Option Skills & Powers