Re: How to improve concentration and attention span
I suggest you to try prayer or meditation on a regular basis. For example, focus on your breath and when you've noticed you've lost attention you kindly bring it back.
There are advanced books on meditation, one such book is The Mind Illuminated if you're of scientific mind. If you'd prefer to get in touch with your more spiritual side I suggest Thich Nhat Han's The Miracle Of Mindfulness.