I love starting a new sketchbook. Its so full of promise. I imagine all the great and still unknown stuff that’s going to go in there. My default sketch book at the moment is an A6 Moleskin plain reporter, normally with a hard cover, as they’re easy to hold in one hand and sketch in surreptitiously. I also like the paper, which takes a pencil well and is nicely absorbent for watercolour. I used to use and sometimes still do use the plain note books from Muji, (148x105mm), which have a similar paper. They have a lot more pages, they last longer, but don’t have the hardback or top hinge. They also use to do an A5 notebook which was great, but they have since discontinued it.