BOOK

This is a selling trade, not a buying one: a Librarian at novice takes 1 books off your hands for a single emerald, rather than handing books out. Anyone crafting bookshelves or an enchanting setup tends to make more books than they need on the way, and this is where the extras turn back into emeralds.

A book itself is cheap to make, just 3 paper and 1 leather, which is exactly why the villager only pays a fraction of an emerald per copy rather than a full one.

One buyer. A Librarian reaching novice, level 1 of five, pays 5 emeralds for 1 books, a rate fixed in the trade file rather than something a villager rolls.

Book also shows up quietly on the other side of his counter: it is the paired ingredient behind every enchanted book he offers, from his very first enchanted book trade at Novice through Apprentice, Journeyman, and up to Expert. Each of those costs the Librarian a plain book alongside the emeralds you pay, though that consumption never shows up as a line item, it just happens behind the trade.

The best rate any villager offers is an emerald per 4 books, from the Librarian, and 1 of the other 3 pays out faster. No villager sells book back, so it is emeralds out and nothing in.

One slot at the Librarian takes 4 books a trade, 12 trades, 12 emeralds. 8 of the 72 villagers that pay emeralds, emptied out:

12 jungle boats against 384 sticks for the same 12 emeralds, 32 times the carrying, and the shortest wait is the Butcher at 7.5 real minutes of shelf, gathering not counted. Book itself pays 4 an emerald, so 13 of the 72 ask less and 50 ask more.

Novice needs 0 banked trading experience, earned from whatever the Librarian sold or bought before that tier, before this book-buying offer opens up.

12 sales close the slot, then a restock brings the same offer back rather than swapping in a different one.

12 sales close the row, needing 2 real minutes idle before it restocks, comfortably inside the 20-minute villager day.

Camp for both refills and one Librarian will take 24 books off your hands across a single Minecraft day, assuming you have that many spare copies to sell.

Sell off spare books after any big enchanting or bookshelf project rather than letting them sit in a chest; this offer converts them straight back into emeralds at 1 books each.

Also on the Librarian's list: ink sac, glass, book and quill, clock, compass, and yellow candle.

A book on its own does nothing, which is why the Librarian buys them rather than uses them. Its value sits in what it turns into. Three books and six planks make a bookshelf, and bookshelves are what push an enchanting table past its low levels: the table reads the shelves standing around it and offers stronger enchantments the more of them it can see.

The second use is the lectern, one book over four slabs, which is both the Librarian's own workstation and the block that makes a village librarian in the first place. So a stack of books is a stack of future villagers, and that is usually worth more than the emeralds the same stack would fetch.

A book is three paper and one leather, and the leather is what makes it awkward. Paper grows back from sugar cane forever; leather comes off animals, which is a farm rather than a field, and it is the reason a stack of books represents more work than it looks like.

Two of them turn into a book and quill with an ink sac, and that is the only writing in the game: signs aside, every word a player leaves behind is in one of those.

A book is also half of an anvil's job. Put one on an enchanting table and it comes out enchanted, which is how a librarian ends up with something worth buying in the first place.

A Book is 3 Paper and 1 Leather, and the Librarian takes 4 Books per emerald. A full restock of that trade is 144 Paper and 48 Leather: sugar cane from How to Build an Automatic Sugar Cane Farm in Minecraft, cows from How to Build a Leather Farm in Minecraft.