This was one of my first books on Buddhism, and it's still a favourite source for ideas and inspiration.
It's divided into two main sections:
1. The three Jewels of Buddhism: the Buddha, the Dharma (his teaching) and the Sangha (community of Buddhists)
2. The threefold path of practice: ethics, meditation and wisdom.
This structure is pretty all-encompassing, and lets you navigate within it very easily.
Each chapter is very short (usually 2 or 3 pages), and can be dipped into without reading the whole book from page one. The text is actually edited down from Sangharakshita's lectures, and it manages to keep the approachability of the verbal format, whilst distilling out his most important ideas in a bite-sized format.
I heartily recommend this book, especially for newcomers or people who want to put their Buddhist readings within some overall framework. Sangharakshita is especially good at presenting Buddhism in a contemporary idiom without losing any of the rootedness in tradition.