Only two of his works have enduring value, his mystical tragedy Merlin, and the part of Muenchhausen called “Der Oberhof” (The Upper Farm), which deals with the lives and types of the small freehold farmers.  Immermann, following Baron von Stein, believed that the health and future of society, endangered by the corrupt and dissipated nobility, rested, on the sturdy, self-reliant, individualistic yet severely moral and patriotic, small peasant.  In the main character of the story, the rugged, proud, inflexibly honorable old farmer, who has inherited the sword of Charles the Great, he has drawn one of the most living characters in early modern German fiction.  The other figures, too, are full of life and reality.  The story has, aside from its importance in the history of the German novel, an enduring value of its own.

Immermann, in spite of his unremitting endeavor, failed to attain literary or moral greatness.  He lacked the fundamental and organic unity of great natures.  He had more qualities of mind than most of his important contemporaries, but in not one of these qualities did he attain to the degree which assures distinction.  In his Merlin he treated a conflict which was fundamentally similar to that of Grillparzer’s Libussa.  Yet Grillparzer, much more one-sided than he, possessed the true Romantic-mystic quality, whereas Immermann had to elaborate his symbolism with the patchwork of careful, allegoric analysis.  He had a richer contact with social forces than Heine, yet his realizations of them were awkward and meagre, his humor wooden, his imagery derived.  He had much greater intellectual force than Platen, yet he lacked the incisive and controlled critical sense of the latter.  Having no one faculty to a distinguished degree, he constantly had to substitute the strained labor of one faculty for the spontaneous production of another.  Predominantly rationalistic, he labored at the symbolistic vision of Romanticism; preeminently a man of prose, he endeavored all his life to be a great poet.  He mistook the responsive excitement produced by the ideas and visions of others for authentic inspiration, the vivacity of a sociable and conversational gift for the creative force of genius, and the immobility of obvious and established conventional judgments for an extraordinary soundness and incisiveness of fundamental analysis.

There was in him, as he himself once said, a certain “aftertaste of a worthy philistinism.”  The dominant bent of his mind was toward the immediate actualities, and this bent in the end, as in his antagonism against the radical students in Halle, always overcame his endeavor to grasp the more remote realities of a larger vision.