在（公司、组织、社团、运动队等的）名册上;受雇;属于officially employed by a company, or an official member of an organization, society, sports team, etc.
There are 256 people on the books at the cement works. 水泥厂的在册员工有256人。
The nursery has 30 babies on the books and 13 on the waiting list. 托儿所的名册上有30个婴儿，等候入托的名单上还有13个。