titles "doctor who the handbook: the first doctor" and "doctor who the handbook: the second doctor", where the colonned-off part is given as the sub-title, are being treated as identical.
I.e. bookcat is not comparing and discriminating between differing sub-titles.
Sometimes a book is re-printed/re-issued with an alternative sub-title (for example here and here. We wouldn't want those to be disconnected on the site, so sub-title changes are probably best ignored.
Having looked at the covers of the two books you mentioned, I think they should be entered differently - which also gets around the problem. See what you think:
's fine by this ppint. - just leaves us hoping future whovers model further handbook item entries on those.
- on the more general point: i dunno. having the two options, of forcing a link between apparently dissimilar book items as examples of one, and that of forcing non-linkinge between two different book items apparently the same from their titles, as separate, (or leaving the default automagically behaviour to operate) seems increasingly attractive - but possibly not an s.o.p., nor a doddle to code, test, debug and beta test.