Much like any Star Trek title, you cannot expect this to be perfect, but simply because of its originality, I had to give this 5 stars.
you have to remember that this was written before most of the alternate and myriad universe titles, so it is of it's time. Nothing like it really existed in the Star Trek novelisations when it came out and because of this, i thought it created its own timeline cleverly when i first read it. The closest genre I would say it could be linked to would be the Myriad Universes books, but this is a whole novel and hence more fulfilling in its length and range of ideas.
I admit that parts are rushed and that it would have done better being longer and creating more depth, but it goes along at a rip-roaring pace in places and as Scotty is the main character in this, you can forgive the failure to create a perfect Kirk. If you are a fan of the scotsman, you'll enjoy his blundering around destroying the timeline just to help out his friend, which is about as Scotty as you can get.
I loved the idea about how the few remaining civilisations in the Alpha Quadrant could survive a full Borg onslaught using a technology already in place in the original pantheon. Moreover, the linking together of many STG concepts really works.
For it's originality alone I give it 5 stars. For writing 3.5 stars. For characterisation, 3.5 stars. But as an overall read, I loved it and this is why the 5.