To start off with, I enjoy the setting of this adventure. Japan in the era of the Warring States feels very original for Doctor Who. Beyond that, a Zen Monastery feels very appropriate for the Seventh Doctor, especially with its koans. (Though the koans all felt very familiar to me; if I had to guess, I'd say Orman got them from Zen Flesh, Zen Bones.) Anywho, some of the more far-flung historicals were a high-point of the New Adventures run.
The TARDIS that we open on is a very somber one. It's clearly a time of endings, and I appreciate that, as we're coming to the end of the New Adventures.
With that said, the Chris subplot is very repetitive. I mean, Roz dies in #56, and then #57 is about him recovering from it. Then Liz sacrifices herself for Chris in #58, and he's again dealing with it in #59. Orman does a great job with the subplot, but it was an ongoing problem with the New Adventures that the character arcs were herky-jerky as if no author read the book that came before theirs (possibly the case).
I could say the same about the Doctor's subplot as, he angsts about regenerating. This idea kept being touched on, as far back as #33 and #36. I suppose you could say he was supposed to regenerate in the 30s, but then held it back so that he could remain Time's Champion, as is stated in #53. But it's another character arc that was dealt with poorly.
With that said, I loved this book's angst about regeneration, because it goes to the heart of regeneration that was revealed in the New Adventures — how the other personalties remain alive within the Doctor's head. So Seven worries about being confined in a little "room with no doors" in the near future.
With all that angst, and with Orman as an author, I was surprised to see The Room with No Doors end on a very upbeat note, as everyone comes to terms with their pasts and future and Seven and Chris have a snowball fight!
Beyond that, good supporting cast. I'd like to see more of both Penelope and Joel. And a decent plot. I gave it a 7+ out of 10.