A Wizard of Mars is the ninth book in Diane Duane's Young Wizards series and continues in the same strong vein as the others. At this point, there isn't much to review in that if you've read the eighth book in a series, it's pretty safe to assume you're going to be picking up the ninth. But in a nutshell, if you do, you'll be rewarded with the same quality you've become accustomed to and many of the same strengths. And if you haven't read the previous eight and are checking out this review simply because it's one of the most recent ones up, then stop reading (possible spoilers) and go pick up book one; it's well worth the time you'll invest as its one of the best fantasy wizard-based series going (and yes, that includes that other young wizard one). You should also know that the series only improves as it goes on. Those nutshell reviews dispensed with, here's the response to A Wizard of Mars in a bit more detail.
The main plot deals with a mysterious artifact found on Mars by a team led by Kit (whose grown steadily more obsessed with the planet). Turns out there's a history of wizards sometimes being able to resurrect "dead" species (it also turns out there are various degrees of "dead") who may have seen whatever calamity that eventually befell them coming and managed to prepare for it. The questions for Kit's team are does the newly found artifact have anything to do with such a process and if so, should the "Martians" be resurrected if possible?
Side plots, as usual for the series, are more interpersonal as the main characters--Kit and Nita--continue to develop personally and magically, as well as with regard to their own long-standing relationship. We also see smaller attention paid to other character development: Nita's father is struggling with his newly widowed status as a single parent, Nita' sister is spending less and less time at home and grieving over the loss of a close friend, Kit's younger sister is still trying to figure out exactly where she fits (not really a wizard but not "normal" either) while his older religious, sister is trying to come to terms with his magical abilities.
The plot takes a little while to get going but then moves along quickly and in interesting, unpredictable direction. One of my personal favorite parts is Duane's use of old-style Martian imagery from film and literature (Burroughs, Wells, etc.) and I wish she had actually given us more of this.
As in earlier books the character development is especially strong as they confront ethical choices, family issues, relationship developments, etc. One of the joys of the series is seeing how these characters change over time--working within a series timeline Duane has given herself the time to develop them slowly and realistically and has the patience to do so. These are also realistic and sharp portrayals of young adults, not some abstract view or an adult's fantasy vision of how young adults act and speak. One example of this is how Duane doesn't simply have them all/speak the same way despite all being "young," but instead gives them distinguishing characteristics according to even small difference in ages. Anybody who is around kids knows there are huge differences between 12 and 14 -yrs-old and 14 and 16-yr-olds, something some authors are seemingly unaware of.
As is typical in the series, the characters grow not simply by being put through their action scenes but because they are often placed in morally grey situations. While this book doesn't have quite the emotional depth of some of the others, this isn't hack-and-slay or Dark Lord bad--Dark Lord opponents good territory. These kids face moral/ethical dilemmas and we get to watch them think their way through them.
There is little to complain about with Wizard of Mars. It's probably a bit too long--there were a few places pacing lagged a little--but a matter maybe of a few dozen pages of cutting rather than a 100 or more as is sometimes the case. As mentioned, I wish she had indulged herself a bit more with the old-style Mars imagery. But these are relatively minor complaints. It isn't the strongest book in the series, but that's a pretty high bar based on just how strong the best books are. It stands pretty well on its own; this is not one of those series where books are seemingly churned out by an increasingly bored author for an increasingly disappointed audience. It continues the series faithfully and leaves the reader wanting to see what these characters will continue to get mixed up with. Recommended and the series highly so.