Did you read the book? If so, would you recommend it?

Yes, its abit long but worth it.

Developing awareness to the unknown in your daily life requires practice, the book with its anecdotes helps in that.

I read the book and recommend it.

That might be an interesting question to ask HN, "How did you find about HN?"

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So if I take the history set of Apps rated/downloaded by a user and give the Apps recommender only half of it to base it's recommendation, is that a prediction engine or recommendation engine?

Prediction. The whole point of a recommendation engine is to change the set of apps you download in the future. Otherwise it might as well not exist!