diff --git a/main.go b/main.go
index 68663e0..6953852 100644
--- a/main.go
+++ b/main.go
@@ -20,6 +20,7 @@ var (
 	ErrInvalidURL      = errors.New("invalid url")
 	ErrNoChaptersFound = errors.New("no chapters found in index")
 	ErrParsingPage     = errors.New("error parsing page")
+	ErrBookNotFound    = errors.New("book not found")
 )
 
 const (
@@ -145,6 +146,9 @@ func (e *Extractor) FetchAndProcessIndex() error {
 	if err != nil {
 		return err
 	}
+	if resp.StatusCode == 404 {
+		return ErrBookNotFound
+	}
 	defer resp.Body.Close()
 	// Parse HTML via Goquery.
 	doc, err := gq.NewDocumentFromReader(resp.Body)