Sum: Forty Tales from the Afterlives message of the book is the importance of exploring new ideas beyond the ones that have been traditionally passed down. The title word "Sum" refers to the Latin for "I am," as in "Cogito ergo sum". Like Italo Calvino's "Invisible Cities", "Sum" does not fit entirely into the traditional category of a novel. "Sum" has been called "philosofiction", an "experimental novel", and "a collection of thought experiments". Most of the stories are understood to "posit the afterlife as mirroring life on Earth" The New York Times Book Review called Sum a "delightful, thought-provoking little collection [which] belongs to that category
Mr. Cogito whose presence is introduced by a poem entitled "Dusza Pana Cogito" (Mr. Cogito's Soul). It brings to our attention Mr Cogito's soul leading a life of its own. In contrast with the souls of the ancient world, it tends to leave him unexpectedly, wandering here and there, oblivious of the owner's well-being. The soul always returns, though, making it possible for Mr. Cogito to adore the world's beauty and diversity in the next poem – "Modlitwa Pana Cogito – podróżnika" ("A Prayer Of Mr. Cogito The Traveller"). This is followed by "Pan Cogito – powrót" ("Mr. Cogito – A Return"),