This reference guide featured in the Tofugu best new Japanese resources in March last year.
The Amazon ebook will be half price until Christmas Eve. So if you usually pay $9.99 it’s $4.99, or 8 EUROs, it’s now 4 EUROs.
Note: It only applies for the ebook and you have to buy through Amazon.
Follow the author’s FB page to hear about these promotions.