I strongly recommend the book 'The Mind Illuminated'. It is written by a neuroscientist who is also an expert practitioner of meditation. That said, it is far less casual than apps like headspace; the principle goal of the book is not to develop increased focus or productivity, but to develop meditation to discover insights into the nature of consciousness through direct experience.

The book does a great job of highlighting many common misunderstandings and pitfalls of beginner mediators in a practical and mostly down to earth way.

I use it with an App called Insight Timer that allows me to track the time I have put into meditating with satisfying statistics and graphs.