minecraft-assets/data/minecraft/recipes/bookshelf.json

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "key": {
    "#": {
      "tag": "minecraft:planks"
    },
    "X": {
      "item": "minecraft:book"
    }
  },
  "pattern": [
    "###",
    "XXX",
    "###"
  ],
  "result": {
    "item": "minecraft:bookshelf"
  }
}