Readers fields are a bit dangerous, you can prevent people (even if they are database managers) from seeing the document.
If there are no readers fields on a document, everyone who has read access or higher in the database's ACL (Access Control List) can see the document.
If all of the readers fields are empty ie "" then again everyone who has read access or higher in the database's ACL can see the document. reference link
Authors fields only apply if the user has Author access to the database.
If a user has Editor access they can edit and save the document.
An Author can only edit a document if their name is in the list of an Authors field.
Having an authors field which is computed on compose to be "@username" allows an author to edit their own documents.
An authors field overrides a readers field, ie if PersonA is in the Authors field and PersonB is in the readers field, PersonA can read the document. reference link
Authors and readers fields can be multivalue.
You can use Groups and people directly in Readers and Authors Fields.
For best results use common names, or even better canonical names. Abbreviated names sometimes do not work. reference link
eg common name: "Adam Foster" Abbreviated: "Adam Foster/AdFos" Canonical: "CN=Adam Foster/O=AdFos"
Best practice for names of authors and readers fields.
Having Readers fields called "Readers" or "Readers_All" or "Readers_Admin" makes finding debugging etc much easier.
Having Authors fields called "Authors" or "Authors_All" or "Author_Admin" makes finding debugging etc much easier.
Best Practice for Readers fields
In the past I have had a computed readers field which checks to see if the other readers fields are not empty, and if they are not empty then the readers field is set to a role "[ReadAll]".
This role can then be used when required to see all documents in a database, very useful if someone leaves and they have otherwise hidden documents.
Splitting the [Admin] and [ReadAll] roles can also be useful when using a database or delegating [ReadAll] .
Servers in the ACL need this role if they are replicating to other servers. Another option is to put "LocalDomainServers" or "LocalServers" in the Readers fields of the documents.