CS Lewis: Cosmic Journeys II

I proposed that seven works by CS Lewis be regarded as a "Cosmic Journeys" series (see here). The series could be published as a tetralogy:

(I) Out Of The Silent Planet.
(II) "The Dark Tower," "The Shoddy Lands" and The Great Divorce.
(III) Perelandra.
(IV) That Hideous Strength and "Forms Of Things Unknown."

The proposed Vol II is what I have called "a Lewis trilogy." The unity of the tetralogy is fairly clear:

(I) begins with Ransom and ends with Ransom writing to Lewis.
(II) begins with Lewis, Ransom and others together and ends with Lewis.
(III) begins with Lewis visiting Ransom and ends with Ransom.

In (IV): That Hideous Strength contains both Lewis and Ransom; "Forms Of Things Unknown" expresses a thought of Ransom in Perelandra.

The proposed Vols I, II and IV are the Ransom Trilogy. If the fragment, "The Dark Tower," had been completed, then it would have become Vol II of the Ransom series although it takes a curious turn because it is neither Ransom nor Lewis but another, younger, character who visits the alternative Earth. Lewis then remains on stage as the cosmic traveler in "The Shoddy Lands" and The Great Divorce before handing the narrative back to Ransom after the opening chapters of Perelandra. Thus, the proposed Vol II, beginning as a continuation from Out Of The Silent Planet, becomes a curious and interesting digression that nevertheless leads the reader back to the expected interplanetary adventures of Ransom in Perelandra.

Lewis corresponds with his friend Malcolm in Letters to Malcolm and somehow accesses a demonic correspondence in The Screwtape Letters. Perhaps he is also the first person narrator who dreams The Pilgrim's Regress. He also at one point converses with Lucy in The Voyage Of The Dawn Treader. Thus, Lewis as character plays an active role, to a greater or lesser extent, in the works of Lewis as author.