The current book volume is Part 4 (第四册, dì sì cè) of the Reading Chinese (如何区分汉语里的形近字, Rúhé qūfēn hànyǔ lǐ de xíng jìn zì) series.
The books in the Reading Chinese series provide you hundreds of frequently used similar looking and easily confused (形近字) common Chinese characters. For the simplicity of the readers, each volume in this series includes about 100 unique characters and nearly 500 explanatory words, phrases, and idioms. All the characters are explained with relevant words, phrases and idioms. Further, all the characters and their explanations are provided with pinyin, and English interpretations.
Online Mandarin Chinese lessons: Ming Mandarin.