The best way I personally have found to consciously ensure I am intaking the information I am reading, and not just skimming it as you said varies between nonfiction, and fiction.
Fiction:
For fiction the best way I found is to either at the end of each chapter, or pages (before you turn the page) is to stop for a bit and think back as to what happened. This allows me to retain what I am reading. I also find this is very interesting method to help your logic skills. I tend to find as I do this I will be either thinking of what is going on and trying to think ahead, or I would try to imagine what I would do instead. Do this practice has allowed me to vividly remember a book I read years ago.
Nonfiction:
For nonfiction I use two techniques that go hand in hand. The first is the same as for fiction, the only difference is that I will stop a bit more often. The second skill is to try to explain what I just read to myself, as if explaining to someone else. This is a way for me to test if I really took in the information I just read, if I find that I can't I will go back and read until I can.
Summary:
I believe that if you make an effort to do this, one; you will find the books WAY more interesting, and two; you will find you brain actually mulling over what you are reading and focusing on it instead of just quickly reading and moving on.
I personally think this come down to your relationship with your client. If they are normally causing you issues with always being on your case about deadlines, getting stuff to them etc. I would recommend keeping this to yourself.
But if they are usually supportive it would not be a bad idea to explain why you would be less available. But as the others said it's your company, run it like you want!