Choosing a notebook for fountain pen ink is easier when you name the problem first. Do you want to avoid feathering, show-through, slow drying, or a pale line? Different paper compromises solve different problems.
Test the exact notebook paper
Write a paragraph with your everyday nib, then make a broad swatch and a reverse-side check. A paper sample from another book is not a reliable substitute because coatings and absorbency can vary between products and page types.
Let the ink dry before judging colour and bleed-through. If the line looks too light, compare the same ink on another paper before changing the bottle. This ink diagnostic keeps paper and nib variables separate.
Feathering, show-through, and bleed are different
Feathering is a fuzzy edge around the line. Show-through means the writing is visible from the reverse side, while bleed-through means ink has travelled through the sheet. A notebook can perform well on one measure and poorly on another.
Decide which side of the page matters for your use. A single-sided work log may tolerate some show-through, while a two-sided planner needs cleaner reverse pages.
Match the notebook to the nib
A fine nib and a wet broad nib ask different things from paper. If you use several pens, test the wettest one you plan to carry. A notebook that handles a fine line may still feather when you use a broad nib for headings.
Record the paper, ink, nib, and drying time beside the sample. The note turns a subjective first impression into a useful reference for the next notebook.
The short answer
Choose a notebook for the failure you most want to avoid, then test the actual paper with your own pen. Compare feathering, show-through, bleed-through, dry colour, and drying time instead of relying on a paper name alone.