diff --git a/lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/librarybook/LibraryBook.java b/lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/librarybook/LibraryBook.java
new file mode 100644
index 000000000..d31daba0c
--- /dev/null
+++ b/lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/librarybook/LibraryBook.java
@@ -0,0 +1,121 @@
+package com.codedifferently.lesson16.librarybook;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class LibraryBook {
+
+  public enum Genre {
+    FICTION,
+    NONFICTION,
+    MYSTERY,
+    SCIENCE,
+    FANTASY
+  }
+
+  private String title;
+  private String author;
+  private Genre genre;
+  private int publicationYear;
+  private List<String> borrowersHistory;
+  private boolean isCheckedOut;
+  private List<String> newBorrowers = new ArrayList<>();
+
+  public LibraryBook(String title, String author, Genre genre, int publicationYear) {
+    this.title = title;
+    this.author = author;
+    this.genre = genre;
+    this.publicationYear = publicationYear;
+    this.borrowersHistory = new ArrayList<>();
+    this.isCheckedOut = false;
+    this.newBorrowers = newBorrowers;
+  }
+
+  public void checkOut(String borrower) throws OverdueException {
+    if (isCheckedOut) {
+      throw new OverdueException("Book is already checked out!");
+    }
+    this.isCheckedOut = true;
+    borrowersHistory.add(borrower);
+  }
+
+  public void returnBook(boolean isOverdue) throws OverdueException {
+    if (!isCheckedOut) {
+      throw new OverdueException("Book was not checked out!");
+    }
+    if (isOverdue) {
+      throw new OverdueException("Book is overdue!");
+    }
+    this.isCheckedOut = false;
+  }
+
+  public String displayBorrowerHistory() {
+    StringBuilder history = new StringBuilder("Borrower History:\n");
+    for (String borrower : borrowersHistory) {
+      history.append("- ").append(borrower).append("\n");
+    }
+    return history.toString();
+  }
+
+  public String getTitle() {
+    return title;
+  }
+
+  public void setTitle(String title) {
+    this.title = title;
+  }
+
+  public String getAuthor() {
+    return author;
+  }
+
+  public void setAuthor(String author) {
+    this.author = author;
+  }
+
+  public Genre getGenre() {
+    return genre;
+  }
+
+  public void setGenre(Genre genre) {
+    this.genre = genre;
+  }
+
+  public int getPublicationYear() {
+    return publicationYear;
+  }
+
+  public void setPublicationYear(int publicationYear) {
+    this.publicationYear = publicationYear;
+  }
+
+  public List<String> getBorrowersHistory() {
+    return borrowersHistory;
+  }
+
+  public void setBorrowersHistory(List<String> borrowersHistory) {
+    this.borrowersHistory = borrowersHistory;
+  }
+
+  public boolean isCheckedOut() {
+    return isCheckedOut;
+  }
+
+  public void setCheckedOut(boolean isCheckedOut) {
+    this.isCheckedOut = isCheckedOut;
+  }
+
+  public List<String> getNewBorrowers() {
+    return newBorrowers;
+  }
+
+  public void setNewBorrowers(List<String> newBorrowers) {
+    this.newBorrowers = newBorrowers;
+  }
+
+  public static class OverdueException extends Exception {
+    public OverdueException(String message) {
+      super(message);
+    }
+  }
+}
diff --git a/lesson_16/objects/objects_app/src/test/java/com/codedifferently/lesson16/librarybook/LibraryBookTest.java b/lesson_16/objects/objects_app/src/test/java/com/codedifferently/lesson16/librarybook/LibraryBookTest.java
new file mode 100644
index 000000000..6ce5bbe5e
--- /dev/null
+++ b/lesson_16/objects/objects_app/src/test/java/com/codedifferently/lesson16/librarybook/LibraryBookTest.java
@@ -0,0 +1,187 @@
+package com.codedifferently.lesson16.librarybook;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.util.List;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class LibraryBookTest {
+
+  private LibraryBook book;
+
+  @BeforeEach
+  public void setUp() {
+    book = new LibraryBook("1984", "George Orwell", LibraryBook.Genre.FICTION, 1949);
+  }
+
+  @Test
+  public void testConstructor() {
+    assertEquals("1984", book.getTitle());
+    assertEquals("George Orwell", book.getAuthor());
+    assertEquals(LibraryBook.Genre.FICTION, book.getGenre());
+    assertEquals(1949, book.getPublicationYear());
+  }
+
+  @Test
+  public void testCheckOut() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    assertTrue(book.isCheckedOut());
+  }
+
+  @Test
+  public void testReturnBook() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    book.returnBook(false);
+    assertFalse(book.isCheckedOut());
+  }
+
+  @Test
+  public void testDisplayBorrowerHistory() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    book.returnBook(false);
+    book.checkOut("Bob");
+    book.returnBook(false);
+
+    String expectedHistory = "Borrower History:\n- Alice\n- Bob\n";
+
+    assertEquals(expectedHistory, book.displayBorrowerHistory());
+  }
+
+  @Test
+  public void testOverdueExceptionOnReturn() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    Exception exception =
+        assertThrows(
+            LibraryBook.OverdueException.class,
+            () -> {
+              book.returnBook(true);
+            });
+    assertEquals("Book is overdue!", exception.getMessage());
+  }
+
+  @Test
+  public void testCheckOutAlreadyCheckedOut() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    Exception exception =
+        assertThrows(
+            LibraryBook.OverdueException.class,
+            () -> {
+              book.checkOut("Bob");
+            });
+    assertEquals("Book is already checked out!", exception.getMessage());
+  }
+
+  @Test
+  public void testReturnBookNotCheckedOut() {
+    Exception exception =
+        assertThrows(
+            LibraryBook.OverdueException.class,
+            () -> {
+              book.returnBook(false);
+            });
+    assertEquals("Book was not checked out!", exception.getMessage());
+  }
+
+  @Test
+  public void testCheckOutAddsToHistory() throws LibraryBook.OverdueException {
+    book.checkOut("Charlie");
+    assertEquals(1, book.getBorrowersHistory().size());
+    assertEquals("Charlie", book.getBorrowersHistory().get(0));
+  }
+
+  @Test
+  public void testMultipleCheckOutsAndReturns() throws LibraryBook.OverdueException {
+    book.checkOut("Alice");
+    book.returnBook(false);
+    book.checkOut("Bob");
+    book.returnBook(false);
+    book.checkOut("Charlie");
+
+    assertEquals(3, book.getBorrowersHistory().size());
+    assertEquals("Alice", book.getBorrowersHistory().get(0));
+    assertEquals("Bob", book.getBorrowersHistory().get(1));
+    assertEquals("Charlie", book.getBorrowersHistory().get(2));
+  }
+
+  @Test
+  public void testBorrowerHistoryIsEmptyInitially() {
+    assertEquals(0, book.getBorrowersHistory().size());
+  }
+
+  @Test
+  public void testGenre() {
+    assertEquals(LibraryBook.Genre.FICTION, book.getGenre());
+  }
+
+  @Test
+  public void testSetTitle() {
+    book.setTitle("Animal Farm");
+    assertEquals("Animal Farm", book.getTitle(), "Title should be updated to 'Animal Farm'");
+  }
+
+  @Test
+  public void testSetAuthor() {
+    book.setAuthor("Aldous Huxley");
+    assertEquals("Aldous Huxley", book.getAuthor(), "Author should be updated to 'Aldous Huxley'");
+  }
+
+  @Test
+  public void testSetGenre() {
+    book.setGenre(LibraryBook.Genre.NONFICTION);
+    assertEquals(
+        LibraryBook.Genre.NONFICTION, book.getGenre(), "Genre should be updated to NON_FICTION");
+  }
+
+  @Test
+  public void testSetPublicationYear() {
+    book.setPublicationYear(1932);
+    assertEquals(1932, book.getPublicationYear(), "Publication year should be updated to 1932");
+  }
+
+  @Test
+  public void testSetCheckedOutStatus() {
+    book.setCheckedOut(true);
+    assertTrue(book.isCheckedOut(), "Checked out status should be updated to true");
+  }
+
+  @Test
+  public void testSetBorrowersHistory() {
+    book.setBorrowersHistory(List.of("Charlie", "Dana"));
+
+    assertEquals(
+        2, book.getBorrowersHistory().size(), "Borrowers history should contain 2 entries");
+    assertEquals(
+        "Charlie", book.getBorrowersHistory().get(0), "First borrower should be 'Charlie'");
+    assertEquals("Dana", book.getBorrowersHistory().get(1), "Second borrower should be 'Dana'");
+
+    try {
+      book.getBorrowersHistory().add("Eve");
+      fail("borrowersHistory should not be modifiable externally");
+    } catch (UnsupportedOperationException e) {
+    }
+  }
+
+  @Test
+  public void testSetNewBorrowers() {
+    book.setNewBorrowers(List.of("Alice", "Bob"));
+
+    assertEquals(2, book.getNewBorrowers().size(), "New borrowers should contain 2 entries");
+    assertEquals("Alice", book.getNewBorrowers().get(0), "First new borrower should be 'Alice'");
+    assertEquals("Bob", book.getNewBorrowers().get(1), "Second new borrower should be 'Bob'");
+  }
+
+  @Test
+  public void testGetNewBorrowers() {
+    book.setNewBorrowers(List.of("Charlie", "Dana"));
+
+    List<String> borrowers = book.getNewBorrowers();
+    assertEquals(2, borrowers.size(), "Should return 2 new borrowers");
+    assertEquals("Charlie", borrowers.get(0), "First new borrower should be 'Charlie'");
+    assertEquals("Dana", borrowers.get(1), "Second new borrower should be 'Dana'");
+  }
+}