Note: PBSS in Geth >=1.13.0 removes the need to prune manually.
Geth (Go-Ethereum) as of July 2022 takes about 650 GiB of space on a fast/snap sync, and then grows by ~ 14 GiB/week with default cache, ~ 8 GiB/week with more cache.
The order book is where users can find data price points of bids and asks. Each price point includes price, count, and amount. This data is useful to traders as it gives them an current market overview.
To get the order book via the API, you may either request it via REST or WebSockets. This guide highlights how to interact with both interfaces. Not only, this guide dicusses a new WebSockets feature: checksums! Now your book will never fall behind.
Using the REST book endpoint is great for those who need a single snapshot of the book.