Gerald North 
Astronomy in Depth [PDF ebook] 

Astronomy in Depth fills the need for a textbook that covers pre-university level Astronomy courses (in the UK, the GCSE syllabuses) and provides numerical examples to help students. It is also written as a serious foundation in Astronomy for amateurs who want to take a more detailed approach than can be found in the bulk of introductory astronomy books. Almost every aspect of astronomy is considered, from Earth and its place in the solar system, through instrumentation, the planets, stars, and galaxies, to black holes and the beginnings of cosmology. This book is perfect for anyone who wants to get to know astronomy in detail, as quickly as possible.