The first is Darwin's On the Origin of Species, adapted by Keller and Fuller. Here, we're on somewhat more familiar ground; indeed, natural history is the one genre of nonfiction which has almost always been heavily illustrated to begin with. Whether by Darwin himself, or other noted naturalists such as Charles Maplestone, John Muir, or Charles Dixon -- or by relative unknowns like John Smith, the field-sketchbook has been an essential part of studying nature in all its forms. Indeed, without illustrations, the value of almost any text of this kind would be greatly reduced.
At the other end of the spectrum, Tara Seibel's version of Freud's 1889 classic On the Interpretation of Dreams brings a visual element to a text that, in many ways, would seem to defeat any endeavor to transpose it into graphical form, unless it be that of a series of talk bubbles coming out of Freud's head! Seibel manages, though, to augment as well as simply illustrate Freud's arguments, bringing a new sort of vision to his iconic work.
Taken together, these two adaptations widen the range of the 'graphic' well beyond the novel -- but do they work? And how do they contrast with the balance of the books, almost all the other contents of which are based on fiction or poetry?