To sum this book up in one word: Pomposity! I realize it was written in 1908, so I'll cut Bennett some slack; however, his arrogant tone throughout made this almost unreadable. He addresses the reader entirely too much "you this" and "you that" and "you know to whom I am referring, oh reader!" What did it in for me was his implication that all who have attended an orchestral concert and did not educate themselves (i.e. have read 'How to Listen to Music') are "[babies] gaping at bright objects." Yes, that's a direct quote.
As for his purpose for writing, he *does* make the good point of having the reader become aware that the "day" doesn't end when the whistle blows for work to end. You've got a lot more time to fill. *HOW* he wants you to fill it, though, is ridiculous.
Also, he makes no bones about it - reading novels (fiction) are useless and a waste of time. Bah! Pompous prig.