Choosing and Using  a Schmidt Cassegrain Telescope
Rod Mollise, the title says it all, if you dont know alot or anything about SCT scopes and are thinking about buying one, then you need to read this book first !

Astronomical Equipment for Amateurs
Martin Mobberley. General discussion on telescopes, eyepieces and other equipment.

Star Testing Astronomical Telescopes
Richard Suiter. Detailed technical book on Star testing. Want to know if your scope suffers from spherical abberation, then this is the book for you. More suited to someone with a science background/knowledge.

The History of the Telescope
Henry King, a comprehensive romp down memory lane of the big telescopes of yester year, their builders and testers. Starting right at the start with Galileo and finishing in the early 20th centuary, a must for anyone interested in telescopes with a view to the past.

Universe in Focus
Stuart Clarke, chronicals and describes the best images taken by the Hubble Space Telescope up until 1997. Also shows how hubble works and the problems it had after launch.

Hubble Space Telescope
Mark Voit, a very large format book showing the best of the hubble images with descriptions, covers up till year 2000. 

Astronomy at Birr Castle
Patrick Moore, small format book discussing the building of the Leviathan of Parsons town (Birr), the astronomy done with the massive 72 inch telescope and how it was and wasnt used up to the start of the 20th centuary, a very interesting read for anyone interested in this telescope and the 3rd and 4th Earls of Rosse.