The Kanji Learner's Dictionary

The Kanji Learner's Dictionary from Kodansha is definitely one of the most essential books for anyone studying Japanese. It's so quick to use that you can start understanding a simple manga or novel even if you hardly know any Japanese grammar.

When you look up a kanji in the Kanji Learner's Dictionary you do it by using the shape of the kanji. There are only four shapes so you can start using the system straight away.

For more details see: http://www.bestjapanesetextbooks.com/kanji-learners-dictionary/ 

Great Japanese Textbooks From Kodansha

There are lots of publishers of Japanese textbooks but I really love Kodansha's Japanese textbooks. Their Japanese textbooks are always very high quality and well-researched, and they are written by some of the best Japanese teachers in the world.

Here's some of the better Kodansha books:
http://www.bestjapanesetextbooks.com/kodansha/

The Most Fun Japanese Textbook For Beginners

If you are just starting to learn Japanese and you want a fun textbook that will keep you motivated to study then you should get "13 Secrets For Speaking Fluent Japanese" by Giles Murray.

I have been teaching Japanese for many years and my students always tell me that this is their favorite textbook. It's full of great hints and tips for learning Japanese quickly and enjoyably.  

The best thing about 13 Secrets is that it helps you to relax and concentrate on communication, not on perfect grammar or finding exactly the correct word. It's a great book for Japanese teachers too!

You can read more about it here: http://www.bestjapanesetextbooks.com/13-secrets-for-speaking-fluent-japanese/

What’s The Best Japanese Textbook For Self Study?

The Japanese textbook book I always recommend  to my students for their self-study is Basic Japanese Sentence Patterns by Naoko Chino published by Kodansha. I think it's the best Japanese textbook for self study.
 
It's a fantastic addition to a more general Japanese textbook that teaches grammar, vocabulary and kanji all together like "Mina No Nihongo" or whatever your teacher uses. There are only three types of Japanese sentence, and Chino-sensei explains the basic 50 patterns and all the variations.

You can read a full review here: http://www.bestjapanesetextbooks.com/basic-japanese-sentence-patterns/