Fat fantasy series are generally
a) longer than 3 books, including different series set in the same world, or they are getting there...
b) fat

AXIS
Douglass, Sara

THOMAS COVENANT
Donaldson, Stephen

DRAGON PRINCE
Rawn, Melanie

DRAGON STAR
Rawn, Melanie

FARSEER
Hobb, Robin

MALAZAN BOOK OF THE FALLEN
Erikson, Steven

RIFTWAR
Feist, Raymond E..

RUNELORDS
Farland, David

SHANNARA
Brooks, Terry

SONG OF ICE AND FIRE
Martin, George R.R.

SWORD OF SHADOWS
Jones, J.V.

SWORD OF TRUTH
Goodkind, Terry

WARS OF LIGHT AND SHADOWS
Wurts, Janny

WHEEL OF TIME
Jordan, Robert