How many books do you typically read at any given time? Do you read one book at a time, completing said book before starting the next, or do you tend to read more then one book at a time?
The only time that I have read two books at the same time as each other was when I left my book that I was currently reading at home, and in a fit of boredom during my lunch break at work I found a book in my car and started to read it. I had my at home book, and my at work book during that time. Otherwise I am a fully dedicated, one book at a time sort of reader. I like to fully immerse myself into a book, and I feel like that would be impossible to do when reading multiple books at once. I have to see my characters through the story before I meet my next family.
Besides, sometimes when it comes to the more tedious classical books you are taking the chance of forgetting the story line if you read it off and on, better to stick with it and see it out. Of course, if switching up helps you through a book that you are finding slow, more power to you.