Kanji Book is described as 'spaced repetition tool to study and review up to 6000 kanji with the help of interactive mnemonics. Your knowledge will be tested using multiple choice questions as well as entering translations in Japanese' and is an website in the Education & Reference category. There are more than 100 alternatives to Kanji Book, not only websites but also apps for a variety of platforms, including Android, iPhone, Windows and iPad. The best alternative is Anki, which is both free and Open Source. Other great sites and apps similar to Kanji Book are Duolingo (Freemium), Memrise (Freemium), RemNote (Freemium) and Quizlet (Freemium).
Anki is a program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.
Have fun while learning a foreign language with Memrise. The more you enjoy learning, the more (and quicker) your skills will develop. This is why entertainment mixed with real-life, relevant content is at the very core of the Memrise language learning experience.
RemNote is the note-taking tool that gives you memory superpowers. It automatically generates flashcards from your notes and figures out the optimal time to practice each flashcard so you don't forget what you've learned.
Vocabulary.com is the easiest, most intelligent way to improve your vocabulary. It combines an adaptive learning system (The Challenge) with the world’s fastest dictionary (The Dictionary) so that you can more quickly and more efficiently learn words.
Learning with Texts (LWT) is a free tool for Language Learning by reading & listening to texts, saving & reviewing vocab. Prerequisites are an installed LAMP/WAMP/MAMP (local web server & database) software and a modern web browser.
Mnemosyne (named for the Greek goddess of memory, Mnemosyne) is spaced repetition software developed from 2003 until the present. The software is similar to SuperMemo, commercial software developed by Piotr Wozniak.