<p><strong>To answer the title question: Yes, all such questions should be community wiki.</strong></p>

<hr>

<p><strong>Proposal</strong></p>

<p>I propose the creation of an exception rule for questions about book recommendations, similar to the one created for <a href="https://stats.stackexchange.com/questions/423/what-is-your-favorite-data-analysis-cartoon/">What is your favorite “data analysis” cartoon?</a> and  <a href="https://stats.stackexchange.com/questions/726/famous-statistician-quotes">Famous statistician quotes</a>.</p>

<p>To ensure a certain quality, the exception rule can only be applied if the following conditions are met (needs discussion)</p>

<ul>
<li>An answer has to provide a at least one paragraph long founded justification why the book is recommended. Answers simply naming the title or stating unfounded reasons ("I liked it") have to be deleted. </li>
<li>Beware of duplicates. Identify them, then merge or delete them without mercy. If possible, merge related questions into a bigger one by broadening the scope of the question to avoid one question for every pair <code>X,Y,Z</code>  where the question pattern is <code>I have expertise in y for x years, which book do you recommend for z</code></li>
<li>All this type of questions needs to be community wiki to prevent the reputation-only-motivation to answer this type of questions</li>
</ul>

<p><strong>Reasoning</strong></p>

<p><em>Recommendations from experts matter</em></p>

<p>No doubt, book recommendations from experts in the particular area are far more valuable than the ones provided by John Smith (no offense to all John Smiths) or the number of the times the book has been bought.</p>

<p>To get such recommendations, one needs ...</p>

<ul>
<li>a site, where experts do contribute</li>
<li>a way to somehow measure the degree of expertise to assign a subjective degree of belief to the recommendations of the recommendation provider</li>
</ul>

<p>Accidentically, stats.SE has both. On the other hand, the review system of a big name book seller, although it might be useful in general, loses more and more of its value if the area of interest gets more and more narrow. Less reviews, less ratings of reviews, etc..</p>

<p><em>Misuse of community wiki</em></p>

<p>We all know: The quality of this site heavily depends on the users learning, accepting and living the rules which have lead to the quality. If the number of users who do not care about the quality in general (!) gets too large, the site is doomed, especially when users with a good amount of reputation do violate the rules in order to farm reputation on their own, hence being a bad example for new users.</p>

<p>IMHO, the current sense of quality in the users with a good amount of reputation on stats.SE is great. On the other hand, stackoverflow (again, only my opinion) is already a big pile of mess with gems hidden in it. I am still able to find the gems, but only due to the search- and "sort by vote"-function. I cannot count the duplicates or the number of times I have stumbeld upon high-level users violating the rules discussed in meta, so I guess that one can get the deputy badge within a day without ease. </p>

<p>So I suspect, that stackoverflow, as the flagship of the SE-sites with the most traffic, requires stricter rules to be sustainable.</p>

<p><em>Summary</em></p>

<p>So: While I agree with most of Robert's arguments, I do not think that such a harsh treatment of book-recommendations questions on stats.SE is necessary .... yet.
If the quality of the site starts to decrease due to heavy misuse we might go back and enforce all these rules. Until then, we should not delete or prevent content which provides actual value. </p>
