Still time to fit in some summer reading if you choose a small-enough book. Here's a few non-fiction recommendations I think you'll enjoy. They are of course, all available on amazon.
Personality by Daniel Nettle: This is not your average woman's magazine article on personality. Rather it's a short tome that engagingly summarizes what science thinks it knows about some basic concepts of human nature and why personality evolved and is so diverse. Great fodder for discussions with partners and friends.
The Chairs Are Where the People Go: by Misha Glouberman - short casual essays by a guy who teaches charades for a living. Ideal for twenty-somethings, but fun and lightly-thought-provoking at any age.
The Happiness Hypothesis by Jonathon Haidt: broader and deeper than most books on happiness, Haidt takes the wisdom of the ancients (greeks, buddhists, etc.) as scientific hypotheses and examines the evidence. Gets a little bogged down in discussing why humans view purity as morality, but overall a great book by a great scholar.
Agatha Christie's Autobiography: by Agatha Christie I expected the grand dame of mystery's autobiography to be full of name-dropping and self-importance - she was after all one of the most successful authors (and women) of the 20th century. Instead it's as readable and flowing as one of her mysteries and a fun way to hear about old times including England in World War II. I was struck by how little she talks about writing, and how she makes it sound like something she did practically on the side while focusing on her husband's archeology career. Insightful and interesting.