I recently finished Lungbarrow, which I chose deliberately as my first foray into the Doctor Who classic novelizations. I'm not sure I would recommend that choice at all. It is very obviously knee deep in book-continuity and starts in the middle of all sorts of action so that I was both very confused and had to look up what the heck was going on.
So, that was a poor choice on my part. However, I don't regret reading it first. There's a reason that you can only find it for 100+ bucks on ebay.
I knew going in that Lungbarrow was a major major source of, well, everything in the Whoniverse. If there's a page on Tardis Wikia that doesn't cite it, it's in the minority. (I'm exaggerating, but only just.) What I did not know is that it is the series closer for the seventh Doctor in novel-form. It tidies everything up and nudges right into the continuity for the 1996 movie - which is apparently unofficially called The Enemy Within. Who knew? Published in 1997, it closed pretty much all the plot threads I didn't even know where dangling.
Honestly, as a book to get into the New Adventures with, I definitely wouldn't recommend it. As a book - without getting into the sticky business of knowing what the hell is going on within the overall story archs - it's absolutely amazing.
Here a bit of thing explaining continuity and discontinuity with, er, spoilers, I guess: http://www.whoniverse.net/discontinuity/NA60.php
And while the BBC did put out an ebook of Lungbarrow, a quick google search might find an ebook version of it for you (scribd has one) since I couldn't for the life of me figure out how to navigate the BBC website to find it. I tried, I did. And I don't really have a hundred dollars to drop on a paperback, even if it does flesh out more of the Doctor Who universe and the Doctor's personal mythology than I've seen anywhere else to date. Of course, that carries the caveat that I'm not done watching all of classic Who.
I really enjoyed the book. It was obvious that it has roots in Gormenghast, which was a bonus, and I was very impressed with all the characterizations of the first Doctor when he was mentioned. Some of the prose gets a little lose, but overall everything ties together and the many perspective changes both make sense and enrich the story.
What was also very interesting is now much the narrative danced around the Doctor's perspective - never giving us a tight third person until near the end, and that every major theme of the mystery of 'Doctor Who?' was touched on at least once.
There was some dissonance for me, however, because the story felt slightly zoomed out - if that makes any sense at all. As if, because there was a lot of ground to cover, that the whole thing needed to be slightly smaller and more abbreviated to fit everything in. I felt that was somewhat of a shame, but then my personal taste runs to more meaty prose and a slightly slower unraveling.
Overall, though, it was a satisfying story. There was a Companion Convergence (where several former companions come together to help the Doctor and meet each other like any good finisher), and it made concrete some of the more interesting aspects of the greater Gallifreyan mythology that I spoiled myself on while reading synopses and behind-the-scenes plot details.
Strangely - and tangentially - reading Lungbarrow gave me greater respect for the plot behind the cheese of the 1996 movie. But I think that deserves its own post.