I can recommend this book. I used it for N5 preparation. The things I most liked about the book are the brief grammar explanations and the tables. I like seeing information organised in tables. If you also like tables, go to a book shop and take a look inside this book.
There is a practice exam at the back of the book. I think the real exam was a little bit more difficult. I started my N5 prep with this book. Then I went on to several other practice materials.
If ordering online, be careful about the language of the explanations. The book is translated in multiple languages. I don’t want you to get stuck with the Vietnamese version if you wanted English.