Angels and Demons by Dan Brown
So this is not directly linked to Kryptos but it does involve some symbol0gy and treasure hunting mystery that would probably interest quite a few Kryptos fans.
The premise of a sharp delineation between science and religion will likely offend any scientists. Fact and fiction are blended together into a Clive Cussleresque novel that will hardly disappoint anyone reading it without expectations of classic literary stylings. For anyone who’s seen the movie Tropic Thunder, the reason this book ultimately fails in my mind is that Mr. Brown “goes full retard”. That may not make sense to some, just know that the book would have been much better without the last 50-75 pages. Dan worked to further convolute the story and lost the chance to make a powerful ending in favor of a twisty and derivative one that will inspire recollections of the Empire Strikes Back.
I included a mention of this book for one overwhelming reason however. Read the book and you’ll realize that the characters operate under misconceptions that could easily be cleared up by talking to someone else or a casual online search. Folks who will have a natural predilection towards trying to solve Kryptos will be tempted to the same mistakes but with less fatal results.
In the end, if you like codes/ciphers/symbology then Dan Brown is not the worst you can do. Approach his books with a little skepticism however because he is talented at twisting things to suit his own purposes.
If you want to save some time though, I’d recommend reading Angels and Demons OR the Da Vinci Code because the plots and characters are practically the same, just switch Illuminati for Opus Dei.