It's hard to review this book without giving away too much of the plot. I'll start by saying the back cover text is a little off. While the plot does involve Scotty attempting to save Kirk from his death on the Enterprise-B, it is not the focus of the book.
One of my few complaints about the book is that DeWeese sets up this interesting situation; what if Kirk hadn't died on the Enterprise-B as seen in "Star Trek Generations"? Kirk doesn't do anything worth mentioning in the plot. He interacts a bit with Picard who appears to look down on Kirk and is jealous because the old Enterprise captain has a close relationship with his crewmen, enough for one of them to want to travel back in time to save him from death. I find that to be a little hard to believe given "Generations" and Picard's willingness to work with Kirk without much complaint. Scotty gets them into the plot only to be reduced to a small role at the end.
Given that main flaw, the book is really about Guinan. She acts as the threat that Picard has to deal with. She leads them into the "alternate universe" that the back cover speaks of. She then holds a secret as to why they are there. The author digs into the character of Guinan, offering an interesting new and fresh look at her. I wish he had gotten more into her, describing her past, perhaps dealing with her life before leaving her planet, her children, her family. There's even an alternate universe Guinan that steps in and shakes things up.
Perhaps another problem with this book is that it reads at times like a fan-fiction more so than a novel. There are cameos galore; Guinan, Sarek, Tal, Kirk, Scotty, the Borg Queen, the Guardian of Forever. Some of these are handled better than others. The entire premise seems to be a time-travel novel that serves as a prequal to both "Generations" and "First Contact." It's not exactly clear until the end of the book how these movies factor in. Most of the novel attempts to continue the events of the TNG episode "Relics," mixing in the new knowledge of Kirk's death and making it all work.
As one reviewer noted, it was nice to have the Borg be true enemies. There are a few plot elements that are never fully developed and perhaps some of that is because of all the time traveling that busies the plot and makes it a little confusing. It was a little frustrating that for a good portion of the novel, the Enterprise-D crew is reduced to Guinan, Picard, Data and brief appearances by Riker and Worf. There were obvious places where Troi's telepathy and counseling skills could have been used more than Guinan's "feelings." With Picard suffering from Borg thoughts, it would have been nice to see someone, Troi, Crusher, Riker, step in and help him through them. Instead, Troi barely appears and Crusher doesn't make an appearance until the final leg of the book.
Given all of this, by the end, the plot does manage to come together. I had a lot of questions, including how Guinan could go the entire book not knowing that the Nexus Ribbon was so close by. Or why Picard didn't seem familiar with Kirk in "Generations" if this had already occured. Or what was the point for Kirk even being included if he wasn't going to do anything in the plot. Or how could an altnerate universe develop advanced weapons when they appear to be lacking resources and they didn't seem to have the same development that we've watched evolve.
Perhaps what holds this book back is that there are a lot of things crammed into the plot that simply aren't explored enough. The author obviously wanted to bring Kirk back from the dead and tie it into the rest of Trek history, yet Kirk's ressurection comes off as just a ploy to get into the situation (or perhaps to get people to buy the book). The focus is obviously on Guinan and her past, but the author fails to take us deeper into Guinan's past when the opportunity is right there. We could have learned more about Guinan, enough to see her family perhaps, to learn about the Borg attacking her planet. This seems to be a revisit to "First Contact" with the Borg haunting Picard's thoughts and the Queen being involved. If the Enterprise and Guinan easily could identify the Nexus Ribbon in "Generations," then why is it such a mystery in this book to them? It too was hardly used to it's full potential.
The book is okay, an interesting read but it ends as if it's more like a sophisticated fan-fic than it does a real professional novel.