The challenging part of this thing is how tiny the details of the printed drawings get when scaled down to fit on the bookmark. No way to get it right with a linewidth of 0,4 mm, it will just pile a heap of plastic. I recommend to go down to 0,2 mm linewidth in the slicer.
That doesn't necessarily mean the nozzle has to be 0,2 mm as well. For me, using a 0,3 mm nozzle worked best as the smaller one easily clogged. A 0,4 mm nozzle will do but you see the difference.
The model is meant for 2 color printing with a single extruder, you change the filament at a certain height. The base has 0,5 mm and then the drawing follows with 0,2 mm.
Slice it with a layer height of 0,2 mm, first layer height 0,3
and in the slicer insert a “Change filament” before the 3rd layer and thus you can print it black on white or what colors you prefer.
This bookmark reuses a printed drawing I made before.
The author remixed this model.