minecraft-kajetans-mod/src/main/resources/data/minecraft/recipes/bookshelf.json

{
    "type": "minecraft:crafting_shaped",
    "pattern": [
        "###",
        "XXX",
        "###"
    ],
    "key": {
        "#": {
            "item": "minecraft:oak_planks"
        },
        "X": {
            "item": "minecraft:book"
        }
    },
    "result": {
        "item": "minecraft:bookshelf"
    }
}