Look here, here, here, here, and here for some interesting pictures of Samuel Beckett's Notebooks.
I find it interesting to speculate whether his doodles have some deeper connection to his writing. There must be literature on this, but I do not know it.
By the way, no Moleskines here, just ordinary notebooks as every kid in France used them. Had he been in America, he would probably have used composition books (which are superior to the ones he did use).