Reviewing The Nth Doctor is really a multi-part operation. First of all, there are the seven different Doctor Who stories that never were, and then there is also Jean-Marc Lofficier's commentary on those same stories. I won't get to spoilers in the first couple of paragraphs, but if you want to be completely surprised by the stories, you might want to skip out later on.
This was a book that Jean-Marc was set up to write, with his involvement in both the workings of Hollywood and Doctor Who (through his Programme Guide) giving him a unique authority on the subject. There was definitely a "need" for a book like this, both because it explains the past and points to the future, and is really one of the last non-fiction books that can be written about Doctor Who.
The background for each of these stories in an interesting insight in how a production is done; after all, most Doctor Who fans, while perhaps experts on Doctor Who, are not experts on how the television or movie industry works. There are three major threads in this book -- the "Daltenreys" thread, the "Dark Dimension" thread, and the "Segal" thread. Especially in the first and last case, we see how a story evolves, ideas mature, and projects fail (in the first two) or partially succeed (the last).
The greatest problem I found with the book is that the temptation to treat all of them as somehow part of the "canonical" Doctor Who universe was impossible -- certainly "The Jewels of Time" will contradict "Fathers and Brothers", and while the elements they all share are important, I found it diverting when a justification about how "these two views do not necessarily contradict". I found it more interesting when there were similarities and coincidences between the different stories; with new emphasis on a more adult relationship between the Doctor, his companions, and the world around him. The focus on the Doctor and his relationship with an evil rival Time Lord -- who was either the Master or the Master in all but name. One of the reasons why the book is fun is that with these different stories from different teams, we get an idea about what "is Doctor Who", something that fans will always argue about.
So, we'll move on to the individual stories -- the good, the bad, and Pog.
The first run of stories started with a standard season 17 script; if someone had told me that The Return of Varnax was going to be novelized by Gareth Roberts, I'd fall for it for a little while. There is really rather little to say about it, as it's a fairly standard Doctor Who story, with Yet Another Mad Time Lord (my biggest fault with the story, as we have all the Mad Time Lords we need that have a long-running relationship with the Doctor). It's a fairly safe Doctor Who story otherwise, and is really therefore not very interesting.
The Time Lord evolves the Varnax story further -- what's interesting is to see how the story evolves. I think Jean-Marc makes too much of the early human / Gallifreyan romance -- after all, the very first Gallifreyan we ever saw in the series fell in love with a human being. I think it's also worth pointing out that it's actually not that controversial for the Doctor to have ex-girlfriends on Gallifrey, as there was certainly a sexual tension between the Doctor and Romana and the Doctor and the Rani. The addition of a romantic subplot in most of the rest of the Nth Doctor stories is a valid theme, and something that I'm sure will be debated as long as there are Doctor Who debates. The Time Lord, like the Varnax story before it, was still nothing that I got excited about, especially when there was little to distinguish that plot from one we might see in the original series.
The Last of the Time Lords however, is where it starts to get interesting. I'm quite fond of the idea that a new Doctor Who starts with amnesia, and the destruction of Gallifrey puts a potential spin on the story that could put a spin on the story that could shock both fans and appeal to a new audience. The idea of making the Doctor an exile -- by the destruction of his home -- is valid where Gallifrey and the Time Lords have become too close and too familiar, but also not rely so heavily on the past to turn off old fans. Out of all of the "Varnax" variations, I like this one the most, and see the most potential springing out of it.
The Jewels of Time still keeps the Doctor fighting an evil Time Lord; an interesting trend in most of the Nth Doctor stories. It's also the best story of the bunch, with an epic feel to it appropriate for a major picture, and it does an excellent effort at bringing the key components of the Doctor Who myth to a new audience without alienating the old. It pulls elements from classic (and not-so-classic) Doctor Who stories like "The Five Doctors", "Deadly Assassin" and "The Key to Time", but also works hard to introduce the character in a way that was faithful to the past but not locked to it. Jewels would be a classic way of tying up the essence of the original series in two hours, and it's tragic that this didn't come together.
It was not tragic, however, the The Dark Dimension ended on the cutting room floor. While it was clever in its use of explaining how an older Tom Baker could still be the Doctor, and unique out of the Nth Doctor stories in having the enemy not be another renegade Time Lord, it is too much the anniversary tale, with Cybermen, Daleks, and Ice Warriors. Oh My! It is perhaps not fair to compare Dark Dimension with the other stories in the book, since the purpose of the story is quite different from any of the others. The interview with special effects designer Tony Harding is also interesting because it reveals a lot about how and why there isn't a pure BBC-produced Doctor Who today. (At least, that's what I got out of it.)
The infamous Fathers and Brothers follows, and it's definitely required reading if you want to attempt to understand Enemy Within. In particular, elements like why the Doctor's eyes were important are better explained here. However, as far as it being "the official EW explanation", I would argue that we can't give too much emphasis or stock on the hows and whys of the Doctors parentage, as it isn't consistent across the various versions of the script, the bible, and the next story. The comparison between the bible for Fathers and Brothers and Andrew Cartmel, Ben Aaronovitch, and Marc Platt's Gallifrey - Notes on the Planet's Background is still a valid one, and I think one of the more interesting points is that both connect the Doctor with the Dark Times of Gallifrey. I felt that Fathers and Brothers didn't quite capture the Doctor Who essence, especially with regards to the placement of "Borusa" as a spirit guide -- the Doctor is the spirit guide, he doesn't need one. I find this so counter to my conception of the character, that it ceases to become "Doctor Who", but instead is a bunch of pod-characters with the same names and the seal of Rassilon. As far as giving the Doctor's wanderings more of a purpose, I found Johnny Byrne's destruction of Gallifrey to be far more effective than searching for papa. Fathers and Brothers is interesting, and has some reasonable ideas (I have no problem with the Doctor and the Master being brothers, and the additions to the design of the Daleks is also not problematic to me) but it's also something I don't regret died before it reached the screen, as it wouldn't have been a Doctor Who I could recognize.
Time of Your Life has a different spin on some of the themes of Fathers and Brothers. With only a few exceptions, I found the story to be more faithful to the original series than Fathers and Brothers, with the removal of Borusa as Spirit Guide and playing down the quest for the Doctor's father. The Daleks should have been called something else -- they struck me as more like Cybermen than anything else, and I think the tie-in to World War II is a nice one. I think some of the concepts about regeneration and timestreams were a little odd, but I think this is also something that may have been better explained in the real script.
The end of the book has two pieces by Jean-Marc on how he might do a few things. The End Of Time was fanfic of the highest order, with obligatory references up and down the shows history. I almost took this as an apology, however, since what it demonstrates is that we can, through a Crisis-style story, retcon *any* new Doctor Who with the original series. I didn't take this as a story that should be told to an audience unfamilar to Doctor Who at all...
The Hand of Omega is exactly the style of story I think a new "first episode" of Doctor Who should have -- starting with the real world, and entering into the Police Box as the story goes on. I was amused by the coincidences with Human Nature as well -- the idea of the Doctor as an amnesiatic teacher works well, of course. (And of course, The Eight Doctors is also supposedly going to have an amnesiatic Doctor.)
In the end, The Nth Doctor is a lot of fun -- by showing the process of how Doctor Who might have started again, we can get a lot of insight about why it is one of our favorite programs. The themes that the different stories have -- even if they don't always get it right, point to what the essence of Doctor Who is all about. It's certainly a recommended book, whether you think you'll like the individual stories in them or not.