[12] In 2005, Cullin published his sixth novel, A Slight Trick of the Mind, a portrait of Sherlock Holmes in old age, for which The New York Times praised the author as being "an unusually sophisticated theorist of human nature,"[13] and Carolyn See of The Washington Post stated that "you don't read it to be 'improved' but for the plain joy of seeing what the language can do in the hands of an affectionate, very accomplished writer.
[16] In April 2012, and to coincide with celebration of National Poetry Month, Cullin published "The House of Special Purpose", a long narrative poem written almost two decades previously and featuring illustrations by Peter I. Chang, which chronicles the last days of the Romanov family during the Russian Revolution of 1918.
[17] From May 2012 to February 2013, Cullin serialized the novel Everything Beautiful is Far Away as an online monthly magazine through the Issuu publication site.
The book was written in collaboration with Peter I. Chang, and featured monthly guest artists and musicians, including Moby, Tsutomu Nakayama, Fights Monsters, Pleq, IP (Identity Problem), Caitlin Kirkley, DJ Terrapin, Chemical Tapes, Wind In Willows, Incompetech, Adriana Pasley, and The Ghost of Mendelsshon.
[20] Along with writers including Salman Rushdie and Amy Tan, Cullin is a founding author of the non-profit Red Room website.