It's hard to recommend just one book. There are a number of suggestions on this Introductory Resources thread: viewtopic.php?f=24&t=148
Personally, I'd recommend Bhikkhu Bodhi's In the Buddha's Words
as a really good introduction to the Buddha's teaching, based on modern translations of a wide variety of suttas.
You can start reading it here: http://www.wisdompubs.org/pages/display ... yValue=104
As far as meditation is concerned, Bhikkhu Bodhi's book contains the most important suttas on meditation. Various teachers flesh these out in various ways. The books I find useful are those that teach similar approaches to my teachers.
Books specifically on meditation that are often recommended include: The Heart of Buddhist Meditation: Satipatthna: A Handbook of Mental Training Based on the Buddha's Way of Mindfulness
, by Venerable Nyanaponika http://www.amazon.com/Heart-Buddhist-Me ... 0877280738Mindfulness in Plain English
by Ven. Henepola Gunaratana
Available on-line here: http://www.urbandharma.org/udharma4/mpe.html
among many others on the link I gave above.