voluminous work; bulky volume; tome
Emphasizes the physical size or length of a book or written work. Often used in formal or academic contexts.
See also: 小著
His voluminous work is in three parts and exceeds two thousand pages in total.
great work; masterpiece; magnum opus
Focuses on the quality, importance, or scholarly value of a written work. Often used for an author's most significant achievement.
This thesis is highly regarded as his magnum opus.