diff --git a/src/app/shared/state/books.reducer.ts b/src/app/shared/state/books.reducer.ts
index 30d5d35..53fe775 100644
--- a/src/app/shared/state/books.reducer.ts
+++ b/src/app/shared/state/books.reducer.ts
@@ -1,4 +1,6 @@
+import { createReducer, on } from "@ngrx/store";
 import { BookModel } from "src/app/shared/models/book.model";
+import { BooksPageActions } from "src/app/books/actions";
 
 const createBook = (books: BookModel[], book: BookModel) => [...books, book];
 const updateBook = (books: BookModel[], changes: BookModel) =>
@@ -7,3 +9,29 @@ const updateBook = (books: BookModel[], changes: BookModel) =>
   });
 const deleteBook = (books: BookModel[], bookId: string) =>
   books.filter(book => bookId !== book.id);
+
+export interface State {
+  collection: BookModel[];
+  activeBookId: string | null;
+}
+
+export const initialState: State = {
+  collection: [],
+  activeBookId: null
+};
+
+export const booksReducer = createReducer(
+  initialState,
+  on(BooksPageActions.clearSelectedBook, BooksPageActions.enter, state => {
+    return {
+      ...state,
+      activeBookId: null
+    };
+  }),
+  on(BooksPageActions.selectBook, (state, action) => {
+    return {
+      ...state,
+      activeBookId: action.bookId
+    };
+  })
+);