Good level design, catchy music, and attractive graphics. The bookcase is well-animated (I never thought I would say those words). Overall, a fun game.
A few considerations for improvement:
The main menu screen does not do justice to the esthetic level of the game, and has a grating music track.
Also, the lethal drops that fall from the ceiling are difficult to see against the background. Anything lethal should have high contrast. (For example, they could be bright red.)
Finally, the controls are OK, but maybe not quite accurate enough for the kind of precision platforming that the game requires. I was unable to cross the long pit where drops are falling from the ceiling and a platform is traveling from left to right.