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.