I do a modification of this meditation as my bread and butter meditation type. Focusing on my breath as you describe is my default. But I allow myself to change focus every now and again. So it might be a touch (e.g. by butt against the floor, a breeze brushing my skin), something I see (e.g. leaves on a tree fluttering, or if eyes closed the light blotches you see through your closed eyelids), a sound (bird tweeting etc), or a feeling (these are the hardest, cos I find it hard to connect with my feelings, and also when meditating that feeling is normally a pretty boring tranquillity, he he). I'll blandly label it as sound/something seen/something touched/something felt....and then I "savour" it, simply allow my mind to focus on it, totally appreciate it, and I'll let myself stay there for a while and then move on to a different focus. If it was a sound and the sound stopped, then I continue savouring that sound in my minds eye. And so it trains mindfulness and focus. I've read a few books on meditation but I think that one came from Dr. Dan Siegel's Mindsight, a great book that explains in simple terms and with loads of real-life clinical examples and practical exercises to practice, the neuroplasticity and psychotherapy science behind meditation.