Shall we use the word hoard? Then we shall use the word hoard. Different books have different functions but I love a little one for notes and a bigger one for thoughts. Little, middle, second from the left, fell into a river with me one time and became swollen and wrinkled like old parchment. It's stained with mould, inside, and appears to have become sentient enough to sketch the scene of its own destruction. Top left travels with me to special places. It has visited mountains in Scotland, river valleys in Spain, deserts in Morocco. Thick, rough paper. It forces me to write slowly. Little, middle, second from the right, flips up like a reporter's notebook from the 1940's. Should be used with a hat, a trenchcoat and a cigarette. The spiralbound ones are old. Rereading their contents reveals the writing of a stranger. The two at the bottom are my current friends and collaborators. Pencil, always pencil.
I rarely ever have pens. As a musician i need to write stuff on music all the time, and also erase it.