Yes, we've had this debate before. Unfortunately, there's no definite consensus to be found about their community wiki status:
Good list, bad list (from July 2013) has the top voted answer (with a meager +11/-2) saying that book recommendation questions need to be actively moderated by the community and should be made community wiki.
The faq post Are resource recommendations allowed? (from August 2013) implements the "Good list, bad list" top scored answer by setting rules for what a good res. rec. answer must contain, and that all answers prior to that policy should be moved to one single community wiki answer that gets an additional notice. No mention of making the question or its policy-conforming answers community wiki is made.
The question Do we need/want an overarching books question? (from December 2013, about the great book list) has no answers of positive score. The great book list itself is closed and has a single large community wiki answer that does not conform to the answer policy, but also lacks the additional notice mentioned in the faq post.
So, already the three main questions I can find on the book recommendation questions disagree on how to exactly handle these questions, or have just largely been ignored. It gets even more confusing when looking into practice:
We currently have 762 questions tagged with resource-recommendation. Many of them are closed as duplicate of the big book list, others as primarily opinion-based, but only 174 of them have been made community wiki. No pattern as to which ones are made wiki and which ones are not is evident to me.1
No pattern as to which ones are closed as duplicates of the book list, which ones are closed as primarily opinion-based and which ones are left open is readily apparent, although the ones to be closed as duplicates of the book list tend to be rather unspecific.
There are 1.063 answers to resource-recommendation questions, of which 544 are community wiki. This indicates that it's mostly the closed questions which are not made community wiki, because the percentage of answers that are wiki is much higher than that of the questions. But again, no clear policy is apparent. Also, I have been unable to find the "additional notice" from the faq post on any old answers.
The amount of answers conforming to the policy set in the faq post is surely debatable, but I'd say at least some of these answers are too short to be considered descriptive evaluations of the books in question.
So, it appears no clear policy exists, or at least, none is enforced in practice. The topic of this meta discussion is therefore:
Should resource recommendation questions be on-topic, on-topic but community wiki, or off-topic?2
1To search for wiki/non-wiki questions, add
wiki:no to your query. Combine with
is:a to get only questions or only answers.
2I have purposefully tried to refrain from making an argument for either case in the question, so that people can vote on the respective answers with their argumentation as they come in.