This is an excellent book, compiled and edited from talks given by Ajahn Sumedho, it is clear concise, and full of insight useful to reflect on, as well as ways to look at the suttas.

The Dhammacakkappavattana Sutta is a detailed explanation of the four noble truths, pointing out twelve 'duties' we have to the truths, and Ajahn Sumedho elegantly uses these are the basis for the investigation into this core teaching of the Buddhas, inviting us to join him in this investigation and see where it takes us, Hopefully to see the truths for ourselves.

Well worth the download, although available in print from related monasteries,