The book is actually also based on comprehensible input. The learning through an SRS happens only for the 1.000 most common words of a language and its grammar

The book is actually also based on comprehensible input. The learning through an SRS happens only for the 1.000 most common words of a language and its grammar. After that, learning is intermixed with speaking, reading, writing and listening to learn vocabulary through comprehensible input. Still, I have to say that learning the top words and grammar, I got to an impressive level, giving the effort. I can listen to some podcasts, read what people write on Facebook and some articles, and speak with friends in noisy contexts.