Temeraire by Naomi Novik (Book #1)

Captain Will Laurence has been at sea since he was just twelve years old; finding a warmer berth in Nelson's navy than any he enjoyed as the youngest, least important son of Lord Allendale. Rising on merit to captain his own vessel, Laurence has earned himself a beautiful fiancee, society's esteem and a golden future. But the war is not going well. It seems Britain can only wait as Napoleon plans to overrun her shores.

After a skirmish with a French ship, Laurence finds himself in charge of a rare cargo: a dragon egg bound for the Emperor himself. Dragons are much prized: properly trained, they can mount a fearsome attack from the skies.

One of Laurence's men must take the beast in hand and join the aviators' cause, thus relinquishing all hope of a normal life. But when the newly-hatched dragon ignores the young midshipman Laurence chose as its keeper and decides to imprint itself on the horrified captain instead, Laurence's world falls apart. Gone is his golden future: gone his social standing, and soon his beautiful fiancée, as he is consigned to be the constant companion and trainer of the fighting dragon Temeraire.