Here's a rum old product line, or at least a rum new one. Alright, easy on the rum there - the sun's not over the yard arm just yet. Mmm, rum. Focus! Ah yes, the joy of weird and wonderful notebooks designed by Octàgon, who evidently also quite like rectangles. Well, what's in a name, eh?
This particular rum punch is mixed from a range of rulings, with a lined index section followed by numbered pages of dot-grid. As the name suggests, such a sub-A5 notebook has a lot of uses, from bullet-journal writing to rough working-out of creative ideas or even, as suggested by the cover, levelling a wonky table. That's a sort of recycling, at least.
So, what should one employ to mark such wibbles and scribbles? This is fairly thick paper with a bit of texture to it, and whether that works with fountain pens depends on the nib and ink flow. With a dry-ish steel nib - which is, to be fair, the set-up favoured by most fountain pen users - the texture is helpful and feathering or bleeding of ink are not major concerns.
With a wet flex nib, the texture is not quite so comfortable to write on and some feathering is evident, although only if you stare hard. If magnification is required to spot a problem, perhaps it's not really a problem, but all the same there may be other notebooks which would have more of a claim on the desk space of fans of 'serious nibbage'.
Of course, there's something else that loves paper with texture, and that's your pencil. So this is pretty much perfect for getting good ideas down quickly, for refinement and subsequent development later on, if you like. Then, if you're an utter barbarian, you can indeed use it to light a bonfire - but don't tell us!