Firstly, if you are a fan of the "The New Doctor Who Adventures" that were published during the 1990's you may be disappointed to note that the reason for the Sixth Doctor to trigger off his regeneration contradicts the reason placed within that series of novels. However, this is an enjoyable romp, and one, which allows the Sixth Doctor to depart on a real high: something that wasn't realised during the television series or the "new adventures" (please debate here).
Of course, one shouldn't simply approach this novel from the regeneration aspect (although it is extremely pleasing that the sixth is allowed to depart on a real dramatic and heroic note), as this is a wonderful novel. The plot reels you in and keeps you hooked. Some may argue that technobabble is abundant. However, I find that it is unobtrusive and adds to the atmosphere and plot rather than getting in the way and having it for the sake of science-fiction necessity. I feel that this novel can be approached for either shear pleasure (i.e. simply an easy and enjoyable read) or you can approach it with the depth that the novel contains and bathe in the (sometimes) complex threads and enjoy the seemingly random plot-lines that tie-up delightfully. This may seem two completely contradictory approaches but honestly, they are both there. Take your pick!
Indeed, there have been better stories. However, that is no reason to decry this is a waste of time: it isn't. I enjoyed it immeasurably and I do strongly recommend that you buy this.