Earth & Sky
Entertaining time travel SF read with an appealingly slow-burn romance and challenging characters. The more action-oriented outer story, a quest for parts of a weapon that will stop aliens from slowly destroying Earth via time-related experiments, ties in nicely to the MC emotional and literal journey to come to terms with her brother's childhood disappearance/death. The alien boy/love interest is the opposite of YA romance genre tropes, not dependable and interested, but essentially using the MC as a tool for most of the plot, while the MC resists developing feelings for Mr. Alien for as long as possible. They both make for more complex, troubled characters than the usual YA heroic fare.
The premise brings back childhood memories of time travel TV minus the on-the-nose educational agenda. Trips to ancient Rome, colonial America and revolutionary France, with a thriller-esque pacing as alien agents chase the leads through time - but the plot does drag a bit, or possibly just not dig deep enough, I never quite worked it out, in the middle.
