Here is another gem from the Smithsonian Graphic Arts Model Collection, a very early — though not the first — guillotine for books or paper. Unfortunately, a fire destroyed the US Patent Office in 1836, so this model is the only remaining record. Visually, it looks much more like the neck cutting variety rather than ones for book or paper cutting. The massive blade operates by gravity rather than a lever or flywheel; again, like the non-book styles. Similar to all the early guillotines is that the blade operates straight up and down.
It’s always a dangerous game to cite the earliest book you have seen that contains this or that evidence, since it often gets superseded. Nevertheless, the earliest book I have seen that contains incontrovertible guillotine marks (thanks to a very damaged blade) is this Harper’s publisher’s cloth binding from 1834 of “The Works of Mrs. Sherwood”. The machine had a clamp and operated straight up and down. The curvature to the marks resulted from tightly clamping and distorting the unbeaten bookblock when cutting, a feature which the patent model above lacks, and when it is released it springs back into its resting shape.
If you have earlier evidence let me know!