The gap between the best bid and the best ask. Buying at once costs the ask and selling at once gets the bid, so a narrow spread means trading in and out costs little.

Can an order on the book fail to fill?

Yes. An offer whose owner no longer holds what it promises is unfunded; it stays listed until a trade reaches it, and then it is removed without filling.

Does the order book show all the liquidity?

No. A token with an AMM pool also trades against the pool, and a trade takes whichever is cheaper at each step, so the real depth is the book plus the pool.

Insights

XRPL Order Book & Market Depth

The XRP Ledger’s exchange keeps an order book for every pair: offers to buy (bids) and to sell (asks), each one an object on the ledger that anyone can read. How to read it, using the RLUSD/XRP book as it stands now.

0.773037

best bid, XRP per RLUSD

0.773993

best ask, XRP per RLUSD

0.124%

spread between them

Bids, asks and depth

Bids: buying RLUSD

Price, XRP	RLUSD
0.773037	58
0.773036	606
0.772960	2
0.772851	10,008
0.772835	9

Asks: selling RLUSD

Price, XRP	RLUSD
0.773993	57
0.774137	2
0.774142	1
0.774160	0
0.774167	1

The five best funded offers each side of the RLUSD/XRP book at ledger 107,734,965, refreshed every five minutes. The full book is on the RLUSD page.

Bids are offers to buy; the highest is the best price a seller can get now.
Asks are offers to sell; the lowest is the best price a buyer can get now.
Depth is how much is offered near the best prices. A trade bigger than the first offers fills against the next ones, at worse prices.

Offers that cannot fill

An offer on the ledger does not lock the funds behind it. If its owner spends them, the offer stays on the book, unfunded, until a trade reaches it or the owner cancels it; a trade that reaches it removes it and moves on (xrpl.org). Right now 1 of the 200 offers listed at the top of the RLUSD/XRP book are unfunded. Offers can also be placed and cancelled within seconds, so a large offer far from the price is not a promise.

The book and the pool together

A token with an AMM pool trades against the pool as well as the book, and a trade takes whichever gives the better price at each step. The depth you can trade into is the book plus the pool (liquidity checker). Before a swap, xrpl.to shows the price impact for your size; a limit order caps the price you accept (limit orders).

Order books through the API

GET /v1/orderbook?base={md5}&quote={md5} returns both sides of any pair with each offer’s account and whether it is funded, for depth charts, spread alerts or a trading screen (API docs).

Questions

What is the spread?: The gap between the best bid and the best ask. Buying at once costs the ask and selling at once gets the bid, so a narrow spread means trading in and out costs little.
Can an order on the book fail to fill?: Yes. An offer whose owner no longer holds what it promises is unfunded; it stays listed until a trade reaches it, and then it is removed without filling.
Does the order book show all the liquidity?: No. A token with an AMM pool also trades against the pool, and a trade takes whichever is cheaper at each step, so the real depth is the book plus the pool.