If you only read one book about science this year, let this be the one. Richard Holmes  has somehow managed to meld a compendium of 18th and 19th century scientific biographies into a compelling narrative that is part travelogue, part scientific exploration, and all magical. He begins with the story of Joseph Banks who travelled the South Seas with Captain Cook as the expedition's botanist, a position he paid for and equipped with many new instruments and two great mastiffs. Banks was one of the earliest westerners to visit Tahiti. He soon learned the language and basically abandoned his botanical studies to become an anthropologist in Paradise.
Banks is also the glue holding this book together. After his years at sea, he settled down and became the President of the Royal Society and eventually funded many of the doctors and scientists covered in this book. The other connecting element here are the Romantic poets. Yes, poets in a book about science! They included Coleridge, Keats, and Shelley--and many less famous ones--who were patients of, and both influenced and were influenced by these scientists especially medical doctors such as Humphrey Davy, John Abernethy, and Sir William Lawrence. The astronomers Caroline and William Herschel also figure prominently here; these two English immigrants transferred from musical careers to discovering planets and comets.
Every page in The Age of Wonder is full of fascinating details. Holmes tells us about Ben Franklin writing letters about the new aeronauts, people foolhardy enough to fly above London in large bags filled with hot air. He also reports that Fanny Burney watched her own mastectomy through a light fabric screen, and describes Davy's experiments with nitrous oxide in which he nearly killed himself and did kill small creatures such as mice and birds.
Another fact that's compelling about this book is how often paradigm shifts must occur before new theories or scientific breakthroughs can happen. Although Humphrey Davy learned through his study of gases that unconsciousness could occur, and though he did mention in his reports that this might be useful in medicine, because the paradigm was that operations must be incredibly painful, it was not until two generations later, that doctors learned to use anaesthesia before operating.
If you'd prefer a longer time frame to view scientific developments, try Patricia Fara's Science: a Four Thousand Year History . For a totally different take on the lives of scientists, you might enjoy Scientific Feuds by Joel Levy.