I can't claim that these are the absolute best popular science books of the year. All that I can do here is to look at the books I reviewed for popularscience.co.uk in 2014 (with the addition one guest title). Any "best of" list has to operate within the subset provided for selection, and this is no different. But I have no hesitation in saying they are amongst the best.
Looking back over 2014, we had a middling year -- not disastrous, but not one that was packed with stand-out, must-read titles. Even so, there are a good few to choose from to add to any respectable popular science collection.