The most-often used route for publishing a book in open access is through an author/editor fee: Book Processing Charge (BPC) for monographs and edited volumes, or Chapter Processing Charges (CPC) for edited volumes; the so-called ‘Gold’ model. Depending on the publisher and the specifics of the book, BPCs may vary widely: fees between €5,000 and €18,000 are most common. CPCs vary as well, typically between €500 and €2000.

Reliable book publishers that offer fee-based open access can be discovered through the Directory of Open Access Books (DOAB), which currently indexes hundreds of publishers.

• Some publishers accept opt-in Open Access for edited volumes, charging CPCs to authors if they wish. This model effectively results in hybrid open access book publications, where parts become freely available online and others remain behind a paywall;  
• Some publishers offer to reduce the BPC/CPC in exchange for imposing an embargo period in which they offer the book for-sale, before opening the contents up. 

These two business models can be criticized for ‘double-dipping’ (i.e. charging both sides of the scholarly communication cycle), and are generally not endorsed by research funders.

• Some publishers offer BPC/CPC-based open access online, and sell print copies of the book alongside.

This business model is generally accepted by funders and in open access policies, because the contents of the work are fully open, and the per-copy costs for the production and dissemination of paper books are evident. Charging the reader for a tangible product is not considered unreasonable.