Books(real books, not your local guys) aren't getting killed. Those of you that believe that are living in a bubble world. They have mathematics on their side. They never have to worry as long as gamblers keep betting.
It is feast or famine for the books but that being said they work on the 5% vigorous i.e..... juice.
They may not get balanced action on each game but they have good and bad days and weeks that all balances out over the course of a season and that is where the 5% works it's self out.
In other words it all comes out in the wash over time.