Pro:
Despite the low price very stable state, even for my rather heavy old 17-inch Notebook
in 7 different positions locked (about 30 degrees to 80 degrees inclination, I guess)
Contraindications:
For books is a Seitenfixierer off (one can submerge luckily, so it does not interfere), which would be good as a stand for thick novels, if not by a part of the last 3 lines would face down.
In the 3 flachereren angle settings an extra part must be folded out, which, unlike the rest, has no rubber feet but hard plastic feet. This was it scratched my wooden desk top when crossed with my notebook. I therefore use since only the relatively steep angle, then there no Problemme because only rubber feet then touch the table.
Conclusion:
Still, I was surprised really positive for the Prei and would recommend it, if you know that you should not take advantage of the shallow angle at wooden tables.