Patterns in the Sky: An Introduction to Stargazing (Night Sky Astronomy for Everybody) A concise guide for learning the constellation including mythology and notable deep-sky objects.
Exploring the Night Sky with Binoculars Everyone's first telescope should be binoculars.
Nightwatch: A Practical Guide to Viewing the Universe [NIGHTWATCH 4/E] A good overview of amateur astronomy beginning with an explanation of the scale of the cosmos and the Earth's place in it.
Turn Left at Orion: A Hundred Night Sky Objects to See in a Small Telescope--and How to Find Them Gives the most honest explanation of what to one can expect to see through a small telescope. Anyone buying a telescope should read this book first.
Collins Atlas of the Night Sky Contains maps not included in Turn Left at Orion: 20 whole-sky star charts and 16 moon maps similar to Rukl's Atlas of the Moon.
A Field Guide to Stars and Planets (Peterson Field Guide) A great reference book for when you need a quick answer. It is small and easily packed so it's perfect for star parties when the Internet is not available.
The Backyard Astronomer's Guide Encyclopedic in breadth. The authors provide links to sources of even more in-depth and current data plus two additional chapters on their website.
The Illustrated Atlas of the Universe A coffee-table book loaded with astroporn: glossy color pictures of celestial objects taken by the Hubble Space Telescope and space probes.