diff --git a/src/models/author.py b/src/models/author.py
index a26c49e..224259d 100644
--- a/src/models/author.py
+++ b/src/models/author.py
@@ -1,12 +1,17 @@
-from sqlalchemy import Column, Integer, VARCHAR
+from sqlalchemy import Column, Integer, String
 from sqlalchemy.orm import relationship
 from sqlalchemy.ext.declarative import declarative_base
 
+from .book import Book
+
 Base = declarative_base()
 
-class Author(Base):
-    __tablename__ = "author"
 
-    id = Column(Integer, primary_key=True)
-    first_name = Column(VARCHAR(length=50))
-    last_name = Column(VARCHAR(length=50))
\ No newline at end of file
+class Author(Base):
+    __tablename__ = 'author'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    first_name = Column(String(50), nullable=False)
+    last_name = Column(String(50), nullable=False)
+
+    books = relationship('Book', back_populates='author')
diff --git a/src/models/book.py b/src/models/book.py
new file mode 100644
index 0000000..c423c32
--- /dev/null
+++ b/src/models/book.py
@@ -0,0 +1,28 @@
+from sqlalchemy import Column, Integer, String, TIMESTAMP, Text, ForeignKey, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.ext.declarative import declarative_base
+
+from .author import Author
+from .book_category import BookCategory
+
+Base = declarative_base()
+
+
+class Book(Base):
+    __tablename__ = 'book'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    author_id = Column(Integer, ForeignKey(
+        'author.id'), nullable=False, index=True)
+    title = Column(String(100), nullable=False)
+    description = Column(Text, nullable=False)
+    year_published = Column(String(4), nullable=False)
+    isbn = Column(String(13), nullable=False, unique=True)
+    status = Column(Enum('available', 'borrowed', 'reserved'),
+                    nullable=False, default='available')
+    created_at = Column(TIMESTAMP, nullable=True, default="CURRENT_TIMESTAMP")
+
+    author = relationship('Author', back_populates='books')
+    # loans = relationship('Loan', back_populates='book')
+    categories = relationship(
+        'BookCategory', secondary='book_category_link', back_populates='books')
diff --git a/src/models/book_category.py b/src/models/book_category.py
new file mode 100644
index 0000000..021b045
--- /dev/null
+++ b/src/models/book_category.py
@@ -0,0 +1,19 @@
+from .book import Book
+from sqlalchemy import Column, Integer, String, TIMESTAMP, Text, ForeignKey, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()
+
+
+class BookCategory(Base):
+    __tablename__ = 'book_category'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    parent_category_id = Column(Integer, ForeignKey(
+        'book_category.id'), nullable=True, index=True)
+    name = Column(String(100), nullable=False, unique=True)
+
+    parent_category = relationship('BookCategory', remote_side=[id])
+    books = relationship(
+        'Book', secondary='book_category_link', back_populates='categories')
diff --git a/src/models/book_category_link.py b/src/models/book_category_link.py
new file mode 100644
index 0000000..f1057d7
--- /dev/null
+++ b/src/models/book_category_link.py
@@ -0,0 +1,10 @@
+from sqlalchemy import Column, Integer, ForeignKey
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()
+
+class BookCategoryLink(Base):
+    __tablename__ = 'book_category_link'
+
+    book_id = Column(Integer, ForeignKey('book.id'), primary_key=True, index=True)
+    book_category_id = Column(Integer, ForeignKey('book_category.id'), primary_key=True, index=True)
\ No newline at end of file