I bought this book just as I was really starting to get into the Big Bang theory, when I'd seen all the episodes and wanted to know more, and it's fantastic!
The book itself is okay quality, the paper inside seems quite thin so there is a risk of tearing, and the whole inside is black and white print, even the photos scattered through the book, except for in the middle where there is a section of colour card photos, about 5 pages I think.
The book is exactly as it says, 'A-Z', there are several things under each letter, and it's all about everything to do with the Big Bang theory, such as Caltech University (Where they work), to Jim Parsons to Chuck Lorre to The Doppler Effect.
Each chapter is filled with loads of information, and I learned a lot, for example, I had no idea that there was an original pilot with a completely different Penny!
Must have book for any fan of the show, easy to read over and over again, fully recommend. :)