[novosel]

Just stating the obvious. All people writing with a fountain pen know that writing in notebooks of any sort is more pleasant when said notebook is rotated 90 degrees, with its spine going across. From left to right.

Then, the angle of the paper to the tip point does not vary across the line.

[dunefox]

Surely you mean 45°? 90° is rather extreme.

[wizzwizz4]

Not if you're writing parallel to the spine.