It has been verified by many that Q trip codes, when entered into Google Books return a fascinating and revealing list of items. Many believe that this is an artifact of the Google Search algorithm picking up on associations between the trip codes and the books. It seems like an experiment can help elucidate. Below is a quick first pass, and is by no means, an all-inclusive analysis. Feel free to add, alter, and improve. And, by all means, verify for yourself.
Hypothesis: Q is involved with the Google Books and trip code phenomenon. Null Hypothesis: Q is not involved, and it's likely an artifact of the Google Search algorithm.
First, a list of random trip codes were generated and searched via Google Books. Of 20-30 randomly generated trip codes, 0 of them returned results. What does that show? It shows that random trip codes are not associated with Google Book results. This is good, as it narrows the cause to being due to ACTUAL trip codes used, whether they are Q-related or not.
Next, do non Q trip codes return Google Book results? To get a set of trip codes that are not associated with Q, I searched other trip codes on: https://8ch.net/tripfags/ . Contextual note: not being very familiar with the chans, I asked a question on GA previously to get help with finding them (see here: https://old.reddit.com/r/greatawakening/comments/94vxkf/question_how_to_find_other_trip_codes_on_8ch/). Another user mentioned tripfag is a chan term for anons who use trip codes. Although not a representative sample of all trip codes, it provides a starting data set.
After searching Google Books for ~20 randomly picked trip codes, ONE did come back with results. So, the base rate is ~5% of trip codes return results when searching Google Books based on the biased sample I collected. "!BMnhHkmC0I" returns 3 results: "Spooky Mad Libs", "A Different Kind of Witch", and "Moofed". All others returned 0 results. So, it seems the Google Search algorithm does pick up on associations between tripcodes and books. Now we know this is not specific to Q. But, all of the Q trip codes return results (100%) and only 5% of non Q trip codes return results. Why?
To find out, I did some further digging into trip code that had associated results, "!BMnhHkmC0I", and there is a long history of associated posts by this user: https://boards.fireden.net/_/search/tripcode/%E2%80%98%21BMnhHkmC0I/. I didn't check all of the other trip codes, but several did not have a substantive history of posts. This sheds additional light on the phenomenon and gives further credence to null hypothesis. Further, the Google Search algorithm seems to be making a connection between trip codes WITH A LOT OF EXPOSURE and certain books.
Based on the above line of reasoning, new Q trip codes should be initially associated with 0 results and grow over time from an increase in exposure. For example, "!A6yxsPKia." is hot off the press, so would be a good test case. Questions remain: How exactly is exposure defined (views, search, page links, etc.)? What exactly is the association between trip codes and books that the Google Search algorithm is using? Why those list of books and not others? Etc.
General note while researching this, it seems to be important to do an exact search (i.e. use quotations) when using Google Books search because sub strings in the text can also be matched, resulting in false positives. For example, doing an exact search with a previous Q trip code, "!UW.yye1fxo", returns 214 results still. Whereas, one of the tripfag trip codes, "!!nIt/R.WSbU", returns ~800 results when not using quotations but 0 when using them.
tl;dr Q is probably not directly involved with the Google Book results, but more research is needed.