The sibling book endpoints — GET /api/v1/books/{bookId}/next|previous and GET /api/v1/readlists/{id}/books/{bookId}/next|previous — differ from the Java version in two ways.
skipRead
The next endpoints accept an optional skipRead query parameter (default false).
With skipRead=true, the endpoint returns the first book after the current one — in series order, or in read-list order — that the requesting user has not read. “Not read” means unread or in progress, matching the read_status search filter.
When every later book is already read, the endpoint falls back to the plain next book, so re-reading a finished series or list still moves forward. Either way it is a single request; without the parameter, clients have to emulate this with extra search round trips.
The previous endpoints do not take the parameter.
numberSort ties
Both directions break numberSort ties by book id, matching the On Deck selection order; the Java version orders and seeks by numberSort alone, so navigation between books with duplicate numberSort is unstable and can diverge from On Deck (gotson/komga#2182).