The 5th Wave, by Rick Yancey

I bought this novel for one of my daughters; she thought she might be bored after work and she seems to enjoy the post-apocalyptic genre.   I couldn't resist reading it before she left town, and it was a fast read.  And an enjoyable one:  even though Amazon calls it a "best teen book of the month" choice, I would not hesitate to recommend it.   I'd expect, for example, that anyone who enjoyed the Wool novels would enjoy The 5th Wave.

The plot basics:  aliens come to Earth; they aren't friendly; things aren't going well for humanity.