My biggest was the Mars Trilogy which over 1600 pages but also read a A Suitable Boy
Other biggie's 1000-1200 were
Phillp Pullman's His Dark Materials as a single volume
Jonathan Strange and Mr Norrell by Susanna Clarke
Quincunx by Charles Palliser
And in the pipeline I have
Mao the Unknown Story by Chang and Halliday
Infinite Jest by David Foster Wallace
The tale of Genji by Murasaki Shikibu