It’s a high-interest topic (aircraft carriers), and a highly-appealing format (the hard-cover book begins with a code that matches it to an online, bilingual e-book).  The introductory page offers instructions for accessing the ebook in both languages (English and Spanish).  The rest of the text of the book is in Spanish only.  The text is simple, and well-supported by the full-page color photos.  Useful both as a tool for Spanish-speaking students who are beginning readers, as well as for those who are learning Spanish.