This meta is based on Chaocipher, a cipher system invented by James Joyce’s friend J. F. Byrne. Byrne actually resided at 7 Eccles Street in Dublin, which is also famous as the Blooms’ address in the novel Ulysses. Chaocipher’s method of operation was not known until fairly recently; you can read the details here, here, or here.
Solvers will note that the set of answers for each town form a pangram, and these answers can be entered in a unique way into the circles (in clockwise/counterclockwise order as indicated by the arc arrows) so as to put a complete set of letters of the alphabet in the 26 outer circles:
The tree and shamrock symbols indicate which side each answer belongs to, but the exact placement of the answers is a bit of a logic problem for solvers. The arrows at the top and the bottom of each ring of circles indicate the “zenith” (position 1) and the “nadir” (position 14) of the disks that form the key in Chaocipher (shown in this diagram, taken from J. F. Byrne’s papers).
The exact working of the cipher involves rotating the disks and permuting the letters on them with each step as letters are encoded or decoded; you can read the details about this algorithm.
Solvers need to decipher the string CRYPTIC NOVEL (given in the flavortext) using the disk configuration provided by the answer letters in the outer ring of circles. Executing the algorithm by hand is somewhat tedious/error prone, but there are easy-to-find computer implementations available on the web, and there is even an online Chaocipher encoder/decoder, so no programming is needed.
Setting up the left and right disks and deciphering CRYPTIC NOVEL yields the meta answer PSYCHO KILMER. This pun refers to another literary “Joyce”: Joyce Kilmer, whose claim to fame is the poem “Trees.”