diff --git a/composer.json b/composer.json
index 6880b6b..507bbc3 100644
--- a/composer.json
+++ b/composer.json
@@ -9,6 +9,7 @@
   "minimum-stability": "stable",
   "require": {
     "php": "^8.3",
+    "jrosset/lasterrorexception": "^1.1",
     "symfony/console": "^7.0"
   },
   "autoload": {
diff --git a/src/Main.php b/src/Main.php
index ad26497..20f9da6 100644
--- a/src/Main.php
+++ b/src/Main.php
@@ -2,6 +2,7 @@
 
 namespace jrosset;
 
+use jrosset\LastErrorException\LastErrorException;
 use RecursiveDirectoryIterator;
 use RecursiveIteratorIterator;
 use RegexIterator;
@@ -103,21 +104,23 @@ EOF
      */
     private function processDirectory(SplFileInfo $directory, OutputInterface $output): void
     {
+        //region Check directory is readable
         $output->writeln('<info>Processing directory: ' . $directory->getPathname() . '</info>');
-
         if (!$directory->isReadable()) {
             $output->writeln('<error>The directory is not readable</error>');
             return;
         }
-
+        //endregion
+        //region Treat each EPUB files (check recursively)
         $directoryIterator = new RecursiveDirectoryIterator($directory->getPathname());
         $directoryIterator = new RecursiveIteratorIterator($directoryIterator);
-        $directoryIterator = new RegexIterator($directoryIterator, /** @lang PhpRegExp */ '/\.epub$/', RegexIterator::MATCH);
+        $directoryIterator = new RegexIterator($directoryIterator, /** @lang PhpRegExp */ '/\.epub$/i', RegexIterator::MATCH);
 
         /** @var SplFileInfo $file */
         foreach ($directoryIterator as $file) {
             $this->processFile($file, $output);
         }
+        //endregion
     }
 
     /**
@@ -132,6 +135,43 @@ EOF
      */
     private function processFile(SplFileInfo $file, OutputInterface $output): void
     {
+        //region Check file is OK for processing
+        $output->writeln('<info>Processing file: ' . $file->getPathname() . '</info>');
+
+        if (mb_strtolower($file->getExtension()) !== 'epub') {
+            $output->writeln('<error>Invalid file extension, "epub" expected</error>');
+            return;
+        }
+        if (!$file->isReadable()) {
+            $output->writeln('<error>The file is not readable</error>');
+            return;
+        }
 
+        $fileParentDirectory = new SplFileInfo(dirname($file->getRealPath()));
+        if (!$fileParentDirectory->isReadable()) {
+            $output->writeln('<error>The file parent directory is not readable</error>');
+            return;
+        }
+        if (!$fileParentDirectory->isWritable()) {
+            $output->writeln('<error>The file parent directory is not writable</error>');
+            return;
+        }
+        //endregion
+        //region Create subdirectory for the file (if necessary)
+        if (count(scandir($fileParentDirectory->getPathname())) > 1) {
+            $fileParentDirectory = new SplFileInfo($fileParentDirectory->getPathname() . DIRECTORY_SEPARATOR . $file->getBasename('.' . $file->getExtension()));
+            if (!mkdir($fileParentDirectory->getPathname())) {
+                $output->writeln('<error>Failed to create subdirectory "' . $fileParentDirectory->getPathname() . '": ' . (new LastErrorException())->getMessage() . '</error>');
+                return;
+            }
+
+            $oldFile = $file;
+            $file = new SplFileInfo($fileParentDirectory . DIRECTORY_SEPARATOR . $file->getFilename());
+            if (rename($oldFile->getPathname(), $file->getPathname())) {
+                $output->writeln('<error>Failed to move file to subdirectory "' . $oldFile->getPathname() . '" => "' . $file->getPathname() . '": ' . (new LastErrorException())->getMessage() . '</error>');
+                return;
+            }
+        }
+        //endregion
     }
 }
\ No newline at end of file