In Dark Mirror, Angel Investigations must face a group of demons capable of becoming duplicates of anyone they get close to -- complete with their personality and memories. The duplicates just happen to reflect their darker, angrier selves. And their duplicates are out to destroy them.
The book is well written and fast paced. The character portrayals are strong and the interrelationships are accurate for the timing of the book (clearly early in season 4).
Gardner does a good job of capturing the strained relationship between Wesley and Angel Investigations, the complex relationship between Wesley and Lilah and Conner's confusion about who he is and what (and who) he should believe.
The ending seems to wrap up quickly (...). But, really, that mirrors the format of a one hour television series, where all is neatly wrapped up in the last 10 minutes. It is, in essence, exactly what we expect and saying that gives away nothing of the plot!
I was a little unclear about how the characters knew how to put a final end to their duplicates (and I won't go into that as it does give something away). I'll just say that I didn't see that part explained -- it may have been edited out or I may just have missed it, as I did read the book in a hospital waiting room.
If you like Angel or Angel books, I'd recommend this book. Its exactly what it should be; a fast paced adventure, true to the characters and the story. Its sure to make for an enjoyable afternoon of reading.