Don't Shoot The Dog, Karen Pryor - this one's not really about dogs. It's about animal training using cognitive learning and positive reinforcement. Pryor was a dolphin and this book is the one that brought clicker-training out of the pool and into the obedience ring, and is a proponent of the nice rather than nasty approach to animal training. If you're wondering whether you'd like to give it a go, it reads a little like Malcolm Gladwell's cod-science books, so if you can happily read The Tipping Point and Outliers, this should be fine for you.
For similar behaviourist-edged writing, but more on traits and less on training, see also Stanley's Coren's The Intelligence of Dogs, which is one of the few places to say sensible things about breed traits.
The Philosopher and the Wolf, Mark Rowlands - I read this last year and mentioned it on the Veggiebox. Much like a canid, Rowlands is self-obsessed but not selfish. His arrogant, egotistical tone takes a bit of getting used to, but is commendable for its honesty and quite refreshing. Here's what Aimee Shalan over on the Guardian made of the book.
King Soloman's Ring, Konrad Lorenz - This is like a blend of the two books I mention above, insofar as it is a scientific book, but concerned with the topic of what it is to be an animal. There are more geese than dogs in it, but it has a lot of personality, and a strong sense of time and place to the anecdotes, which add to the interest. Lorenz was one of the fore-runners of modern ethology, which is where my own main area of interest in animal psychology lies. Lorenz won the Nobel Prize for Science and Medicine in 1973.
The Hidden Life of Dogs, Elizabeth Marshall Thomas. I've only just found out that Marshall Thomas is actually a novelist. I'm keen to check out her. She's one of the modern breed of ethologist. This book is about the development of a pack of dogs, including a dingo or two, she shared her life with. Hers and Rowlands' are the most pleasurable reads here, great books regardless of their subject matter. I'd actually highly recommend The Tribe of Tiger, her book on cat behaviour, but as we were talking dogs here...