i want to improve my photography knowledge. i have read "understanding exposure" which was nice one and some others, so were really useless and waste of time. so can you recommend something that really helped you become a better photographer (not for beginners). in other words, the best book you read about photography.
If the mechanical/technical aspects are also important in addition to the inspirational/art portion, "Photography" by London, Stone, Upton has passed the test of time, though be aware it is principally geared to film, but the real aspects of photography apply to film and digital alike.
Well it is a very narrow topic, but I really got a lot out of "Bystander, a History of Street Photography." Also recently read "Hurrell's Hollywood Portraits" which was great. Neither are educational in nature, but you learn by seeing what others have done, why, and somewhat how...but mostly the "how" of it you have to figure out yourself. Also some of the Ansel Adams books are great, as well as those of Cappa and the founding of Magnum...much of which is covered in Bystander. I started a couple of books on Annie Leibovitz but I found the whole think so self-indulgent that I was not interested in finishing either...but that is just me of course. Oh, studying the works of Henri Cartier-Bresson helped me see photography differently too...of course becoming different is far more difficult than being inspired. But seeing this in a new light has been a help.
A book that really helped me out when I was starting was "PC Magazine Guide to digital photography" by daniel Grotta. This helped me learn about aperature and shutter and such. Whats REALLY weird is when I got to the end of the book one of the images was of a friend of mine!!! not sure how he got in there but whatever.
Don't forget the classic 3--volume set from Ansel Adams: The Camera, The Negative, The Print. Although obviously geared to film photography, there's a lot to learn from here.