I tend to divide 1E AD&D into 3 eras:
Early AD&D is roughly 1977-80 and consists generally of the Monster Manual, Players Handbook, Dungeon Masters Guide, Deities & Demigods, World of Greyhawk folio, early modules (A1, C1-2, D1-3, G1-3, Q1, S1-3, T1) and accessories (The Rogues Gallery, etc.), and Dragon magazine when it was still The Dragon (up to #38, June 1980).
Mid AD&D is roughly 1981-85 and consists of the reprinted core rulebooks and modules, Fiend Folio, Monster Manual 2, Unearthed Arcana, Oriental Adventures, the World of Greyhawk boxed set, Lankhmar: City of Adventure, the Battlesystem boxed set, a ton more modules (A2-4, C3-5, CA1, CB1-2, DL1-11, EX1-2, H1, I1-7, L1-2, MV1, N1-2, S4, T1-4, U1-3, UK1-7, WG4-6) and Dragon issues 39-104 (in which, it should be noted, much of the material from MM2, UA, and the WoG boxed set originally appeared).
Late AD&D is roughly 1986-88 and consists of cheap reprints of the rulebooks that fell apart if you looked at them wrong, 'supermodule' compilations (A1-4, GDQ1-7, I3-5, I12, S1-4), Dungeoneer's Survival Guide, Wilderness Survival Guide, Manual of the Planes, Dragonlance Adventures, Greyhawk Adventures, the Forgotten Realms gray-box, City System, Kara-Tur: The Eastern Realms, the Dungeon Master's Design Kit, a bunch more modules (C6, CA2, DL12-16, DQ1, FR1-6, FRC1, H2-4, I8-14, N3-5, OA1-5, OP1, REF3-5, RS1, WG7), Dragon issues 105-150 (or whenever the 2E transition occured), and Dungeon #1-20 (or thereabouts).
The first period is (IMO) pretty much pure gold and is generally what I'm thinking of when I refer to "AD&D." The second period is a decidedly mixed bag, with some great stuff (mostly the Gygax Greyhawk stuff) offset by an increasing proportion of dreck (like the Conan modules, or that stupid "magic viewer" module, and of course Oriental Adventures). The third period is (again IMO) almost a total wasteland without a single item that I would consider a true classic, and only a small handful of items I'd even consider worth owning at all.
Early AD&D is roughly 1977-80 and consists generally of the Monster Manual, Players Handbook, Dungeon Masters Guide, Deities & Demigods, World of Greyhawk folio, early modules (A1, C1-2, D1-3, G1-3, Q1, S1-3, T1) and accessories (The Rogues Gallery, etc.), and Dragon magazine when it was still The Dragon (up to #38, June 1980).
Mid AD&D is roughly 1981-85 and consists of the reprinted core rulebooks and modules, Fiend Folio, Monster Manual 2, Unearthed Arcana, Oriental Adventures, the World of Greyhawk boxed set, Lankhmar: City of Adventure, the Battlesystem boxed set, a ton more modules (A2-4, C3-5, CA1, CB1-2, DL1-11, EX1-2, H1, I1-7, L1-2, MV1, N1-2, S4, T1-4, U1-3, UK1-7, WG4-6) and Dragon issues 39-104 (in which, it should be noted, much of the material from MM2, UA, and the WoG boxed set originally appeared).
Late AD&D is roughly 1986-88 and consists of cheap reprints of the rulebooks that fell apart if you looked at them wrong, 'supermodule' compilations (A1-4, GDQ1-7, I3-5, I12, S1-4), Dungeoneer's Survival Guide, Wilderness Survival Guide, Manual of the Planes, Dragonlance Adventures, Greyhawk Adventures, the Forgotten Realms gray-box, City System, Kara-Tur: The Eastern Realms, the Dungeon Master's Design Kit, a bunch more modules (C6, CA2, DL12-16, DQ1, FR1-6, FRC1, H2-4, I8-14, N3-5, OA1-5, OP1, REF3-5, RS1, WG7), Dragon issues 105-150 (or whenever the 2E transition occured), and Dungeon #1-20 (or thereabouts).
The first period is (IMO) pretty much pure gold and is generally what I'm thinking of when I refer to "AD&D." The second period is a decidedly mixed bag, with some great stuff (mostly the Gygax Greyhawk stuff) offset by an increasing proportion of dreck (like the Conan modules, or that stupid "magic viewer" module, and of course Oriental Adventures). The third period is (again IMO) almost a total wasteland without a single item that I would consider a true classic, and only a small handful of items I'd even consider worth owning at all.