How many bookshelves for level-30 enchanting?

15 shelves, with one empty block between

Fifteen correctly placed ordinary bookshelves give an enchanting table its maximum bookshelf power. A simple setup is a 5 × 5 perimeter around the table, leaving the inner ring empty. Here is a top view at table height: B is a bookshelf, T is the enchanting table and a dot is empty space.

B B B B B
B . . . B
B . T . B
B . . . B
B B . B B

The rows contain 5 + 2 + 2 + 2 + 4 = 15 shelves. The bottom opening is the entrance. This is a countable construction diagram, not a screenshot of a tested world. Keep the gap clear rather than guessing that a decorative block is transparent enough. Use ordinary bookshelves; chiseled bookshelves are a different block.

Materials for this layout

Fifteen bookshelves require 45 books and 90 planks. If crafting all 45 books from paper and leather, that is 135 paper and 45 leather. The enchanting table itself is separate: one book, two diamonds and four obsidian.

What “level 30” does and does not mean

The bottom offer can require experience level 30. Selecting that offer uses three experience levels and three lapis, so having exactly level 30 leaves level 27. The requirement is not a 30-level charge. You still need an eligible item and lapis in the interface.

The table does not award a fixed “two levels per shelf” independently of its roll. More than 15 effective shelves does not increase the capped bookshelf power. Maximum bookshelf power does not guarantee a particular enchantment, the maximum level of every enchantment, or a treasure enchantment such as Mending.

If the third offer is too low

1. Count the actual shelf blocks; do not count floor decorations or empty positions.
2. Check that the table is centered and that the one-block gap is clear at the relevant heights.
3. Try the simple single-height layout above before adding a decorative second row.
4. Check the actual offer on an eligible item, then confirm your experience and lapis. A server or datapack may use different rules.

Source: Minecraft Help: getting started with enchantments documents the 15-shelf, 5 × 5 arrangement and recipes. The diagram and material totals above are our explicit construction and arithmetic.