Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Ref_document_types ( document_type_name VARCHAR, document_type_code VARCHAR )
TABLE: CREATE TABLE All_documents ( document_type_code VARCHAR, document_name VARCHAR )

### Question ###
What is the document type name for the document with name 'How to read a book'?

### Accurate SQL ###

SELECT T2.document_type_name FROM All_documents AS T1 JOIN Ref_document_types AS T2 ON T1.document_type_code = T2.document_type_code WHERE T1.document_name = "How to read a book"