If you have somehow stumbled upon this review please be warned that it may contain spoilers from the first book. If, for some reason, you have not read the first book, please do so - it's bloody brilliant.
It is my misfortune to report that Scott Lynch has been diagnosed with SBS (Second Book Syndrome). Symptoms include the second book not living up to the first. Readers may expect disappointment and a general feeling of being underwhelmed.
Joking aside "Red Seas Under Red Skies" is, in its own right, a fantastic book and I think this one will grow on me when I read it again (and again). Where the book falls down is the plot, but it shines because of the characters, particularly the charismatic and loveable Locke Lamora.
Whilst The Lies of Locke Lamora is exploding (literally in some parts of the story) with action, RSURS bumbles along at a more mellow pace with the plot spread over several weeks, as opposed to a few days in the first book. It's the pace that lets the book down in the end - many pages are devoted to Locke and Jean learning how to pirate, which dampened the excitement induced by the beginning of the book.
However, the book's strength lies in the characters. We are introduced to some badass female characters (Delmastro, Drakasha and Selendri) - it's refreshing to come across female characters who have a purpose beyond being love interests (I had a bad experience of this recently).
We do see a different side to Locke though. It's clear that he's still getting over the pain of losing the majority of the Gentleman Bastards and Lynch does this perfectly. Sometimes Locke's pain is raw and obvious, at other times its subtle - he pushes people away, he's distrustful, quite reckless at times and full of vengeance.
Although RSURS doesn't match up to the pace and the action of the first book, I did enjoy the subtleties playing behind the scenes. I have high hopes for the rest of the series though and cannot wait for the third book :D