The Royal Astronomical Society Observers Handbook and Calendar are the most useful handbook and calendar I have used. The handbook includes information on the Sun, Moon, planets, comets, stars, and deep-sky objects. It includes also a monthly sky guide, articles on optics and observing, among other topics. The calendar shows the phases of the Moon as well as the time of sunrise, sunset, moonrise and moonset, and interesting observing events.Introductory Books on Astronomy
Nightwatch - An Equinox Guide to Viewing the Universe by Terrence Dickinson. This highly recommended book is one of the best introductory texts written on astronomy, with lots of helpful information on learning the sky, telescope equipment, deep-sky objects, comets, moon and planets, and astrophotography. Useful even for observers who have been in astronomy for a while.
The Light Hearted Astronomer by Ken Fulton. A humorous and somewhat tongue in cheek view of the pitfalls of being an amateur astronomer. It is full of very useful advice. This book had been out of print but it was recently announced that it has been updated for 2015.Books on the Astronomy Equipment
The Backyards Astronomers Guide by Terrence Dickinson and Alan Dyer. The companion book to NightWatch that goes into much more depth.
Star Testing Astronomical Telescopes - A Manual for Optical Evaluation and Adjustment. by Harold Richard Suiter. Detailed instructions on using the star test to determine the optical quality of a telescope.
Telescope Optics, A Comprehensive Manual for Amateur Astronomers by Rutten and van Venrooij. An analysis and comparison of the many different telescope types available on the market today.Books on Amateur Telescope Making
Build Your Own Telescope - Complete Plans for Five Telescopes You Can Build with Simple Hand Tools by Richard Berry. Very complete book on building five different telescopes and mounts with detailed instructions and illustrations. The Dobsonian-style mounts I built for two of my refractors are based on plans from this book.
The Dobsonian Telescope by Kriege and Berry. Detailed instructions on how to build state of the art Dobsonian telescopes.Books on the Deep-Sky
Burnham's Celestial Handbook - An Observers Guide to the Heavens by Robert Burnham, Jr. Somewhat dated material but still a handy reference to have around.
The Messier Album - An Observers Handbook by John Mallas and Evered Kreimer. Contains detailed descriptions of the Messier objects including sketches and photographs. Considered a standard reference on the Messier's until Stephen James O'Meara's book was published.
Celestial Sampler by Sue French. This book includes a number of essays from her column in Sky and Telescope magazine, as well as sketches made at the eyepiece.
Deep-Sky Companions: The Messier Objects by Stephen James O'Meara. Like the book on the Messier's by Mallas and Kreimer contains descriptions of the Messier objects including sketches and photographs. However has been updated with the latest information on the Messier objects and translation of Messier's original observations. The book includes sketches of the Messier's and observing tips. He published another book entitled Deep-Sky Companions: The Caldwell Objects which includes another 109 deep-sky objects, many of these discovered by William Herschel.
Deep-Sky Wonders by Walter Scott Houston. These are a selection of some of Scotty's columns from Sky and Telescope Magazine with commentary by Stephen James O'Meara. Scotty wrote the column from 1946 to 1994, and having many of them presented in a month by month guide makes a very useful reference guide.
The Year-Round Messier Marathon Field Guide by Harvard Pennington. A nice field guide for locating the Messier objects including finder charts and sketches of each object.
The Night Sky Observing Guide by George Robert Kepple and Glen W. Sanner. A very comprehensive guide for deep-sky objects, giving detailed information on thousands of galaxies, nebula, star clusters, and stars, as well as sketches and photographs. Geared towards larger aperture telescopes; in practice I find detail can often be seen in smaller aperture telescopes as well.
Uranometria 2000.0 Deep-Sky Atlas by Tirion, Rappaport, Remaklus. Volume 1 covers the northern sky, volume 2 the southern sky, and volume 3 is the deep sky filed guide. Very detailed star atlas and field guide that contains over 280,000 stars and over 30,000 deep-sky objects on highly accurate maps.Books on the Planets and Moon
The Planet Saturn by A.F.O'D Alexander. A very detailed history of Saturn observations, theories, and discoveries.
The Planet Observer's Handbook Second Edition, by Fred W. Price. A good general reference book on the solar system, including historical observations.
Observing and Photographing the Solar System by Thomas Dobbins, Donald Parker, and Charles "Chick" Capen. A good general reference book on the solar system, including an introduction to astrophotography.
Astronomical Tables of the Sun, Moon and Planets Second Edition, by Jean Meeus. A very handy reference book to have that includes many past and future astronomical events.
Atlas of the Moon by Antonon Rukl, Director of Prague Planetarium. A very fine lunar atlas. Sky and Telescope sells a fold up lunar map by Rukl that is handy to have at the eyepiece.