I just read this book, and loved it. The mystery was well done, I thought.
I have questions about two points in the book. First, the sequence of symbols that Seldom says is so basic. M, heart with underline, 8, ??? What is the fourth symbol? It’s supposed to be simple, but I can’t figure it out and it’s driving me crazy.
Second, the Assyrian frieze Seldom talks about at the end. He tells a story about the hidden story within it. Is this true? Is there more information about this available somewhere?
I’ve not read the book, but what you’ve described is a fairly old puzzle, and the answer is:
The symbols are the positive integers (1, 2, 3, …) combined with their mirror-images as reflected in the line down their left sides. Easier to draw than describe in words, but if you look at “2” it’s like the right side of a heart with a line underneath it, right? Put a backwards “2” in front of it, and it makes a whole heart underlined. Likewise, a reversed “3” before a normal “3” makes a fat “8”. So, the next symbol in sequence will be a backwards “4” followed by a normal “4”, and looks like an “M” with a horizontal line extended through it about half-way up.
If it’s any consolation, it initially stumped Lisa, the smartest member of The Simpsons, too. (Season 8, Lisa the Simpson.)