The Eighteen Carefully Sorted Books

I will here propose you $$9$$ ways to sort $$18$$ books. Those books remain the same. For each $$9$$ ways you have to tell why this is a sort over this books. Meaning:

• There is no Bookleft > Bookright > Bookleft
• There is no BookA left = BookB left > Bookright (Bookleft is always greater than Bookright)

Some ways are very easy to find out, some are very tricky. You are not intended to find all (without this being forbidden haha). If you found one or just a few you can add an answer, just check it wasn't already told, and if so, do not hesitate to +1 the writer's answer or cite him :p.

This is a Lateral-Thinking Puzzle, so I did sort my books in certain ways, but it is possible, that you find other definition that match my sorts, as long as you can justify and that is a clear sort as previously defined, it is perfect :)

There is an icing on the cake at the end!

Sort 1

Solved - Glorfindel

Sort 2

Solved - user65284

Sort 3

Solved - Glorfindel

Sort 4

Solved - user65284

Sort 5

Solved - Gareth McCaughan

Colors related

Sort 7

Hint - 12th May 2020

Apart for the books' order, there is something different from this picture.

Hint - 21th May 2020

You may need all other books' pictures to find this one!

Numbers related

Alphabet related

Meta Sort

It's not a sort on the books, but the idea of a meta sort came in comment, from @JMP, and I thought it'd be a good idea adding it to the puzzle. Could you define a meta sort on all the 9 sorts, how are they sorted within themselves? That will be another part of the puzzle when all the 9 sorts will be found!

Icing on the cake

There are two books that can't be easily identified. The big red one and the thin light blue one. The icing on the cake, consists, thanks to the nine sorts, to find which books they are. I'm just curious to know if someone will succeed. It's not properly part of the puzzle, I'm not even sure this is possible without knowing the books :)

Hints and selected answer

I've added some hints (12th May of 2020) for remaining sorts. I've decided to give someone a selected answer based on the following points system:

• 1 point per sort firstly discovered before 10th May 2020 (one month before puzzle release)
• 2 points per sort firstly discovered after 10th May 2020
• 5 points for finding meta sort first and 5 points for icing on the cake first.
• Selected answer given when all 9 sorts discovered and selected answer will adapt after that, depending on standings.

I created this point system with my own opinion on this puzzle hardness but if you have any suggestions to edit it, don't hesitate adding a comment. Ties will be untied with icing on the cake more important to solve, then meta sort, second more important to solve.

Current standings are - 12th May:

1. user65284 - 2 points (draw) Glorfindel - 2 points

3. Gareth McCaughan♦ - 1 point

• @Glorfindel; I think he means the 'meta'-sort - how the sorts are ordered within themselves. – JMP Apr 10 at 13:32
• The thin blue book appears to be: (rot13) Cerzvre Nzbhe by Vina Fretrlrivpu, Ghetrari: amazon.com/dp/1544077203 – Nick Apr 10 at 19:37
• Almost certainly not :P, you can see enough of the blue one in sorts 1 and 2 to figure it out without knowing anything about any of the other books, there's nothing giving away the red one – Nick Apr 10 at 19:42
• I'm sure they do, however I meant visual distinctions looking at the books in isolation, not where they are in sort order, I see nothing but a red, glossy, hardback book ^^. To give you an idea this was all I needed to find the blue book: (rot13) "cerzvre nzbhe" "rager znvagf" obbx ;) – Nick Apr 10 at 19:45
• @El-Guest, Because I miscounted! Thank you ;) – JKHA May 12 at 20:50

3 Answers

Sort 5

The person who said "publication date" for this one was almost right. It's in descending order of (first) author's birth date.

I rather expected

one of the orders to have the books sorted by either title or ISBN, but that seems not to be.

Number of pages

Sort 4

First name of the author (The real name of Voltaire is François-Marie Arouet)

Sort 5 (Incorrect)

Publication date (of original edition)

Sort 6

Color - Maybe the flag of France?

• You found the same sort as me for Sort 2 and 4! For Sort 5, yours isn't correct: you can check at several instances, it won't match, for example Derobert (2010) $\ngtr$ Solès (2018) $>$ Ankaoua (2016). For Sort 6: you are correct and I didn't think of France's flag, I like it a lot! – JKHA Apr 10 at 16:07
• @JKHA I'm surprised the French flag was accidental, given that most if not all of the books appear to be French, as are you yourself based on your profile. Blame it on your subconscious maybe? – Darrel Hoffman Apr 10 at 18:52
• @DarrelHoffman, haha! I was thinking of another sort indeed, and I'm also surprised I didn't see that before user65284! I think seeing the French flag since my youngest days may have influenced me indeed... Subconscious yes! Rightly said ;) – JKHA Apr 10 at 19:22
• This can’t be the answer for 6, though, right? Because then you could arrange the blue books in any order, etc... – El-Guest Apr 13 at 4:00
• @El-Guest, exact El-Guest ;) – JKHA Apr 15 at 0:00

Well, for starters, sort 1

by book height (the tallest one first, the shortest one last)

and sort 3

looks to be sorting by last name of the author (Ankaoua is the first one, Voltaire the last one)

Observation for sort 8:

All books with a number on the back are on the left, and they seem to be sorted (though I'm not sure how to arrange the numbers on the first three): 10 18 1 84 4645 > 10 18 1 84 4605 > 10 18 1 84 4604 > 17247 > 1446 > 1325 > 4 > 2 > (no number)
How the remaining half of the books is sorted, I don't know ...